The On-Line Encyclopedia of Integer Sequences (OEIS)

Revisions by Chai Wah Wu

(See also Chai Wah Wu's wiki page)

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A381511

Smaller of two consecutive primes p and q, both ending with 9, such that q-p = 10n, or -1 if no such primes exist.
(history; published version)

#14 by Chai Wah Wu at Sat Mar 08 21:06:15 EST 2025

STATUS

editing

proposed

#13 by Chai Wah Wu at Sat Mar 08 21:06:11 EST 2025

PROG

p += 10 # Chai Wah Wu, Mar 08 2025

#12 by Chai Wah Wu at Sat Mar 08 21:05:59 EST 2025

PROG

(Python)

from sympy isprime, nextprime

def A381511(n):

p = 19

while (q:=nextprime(p)):

if q-p == 10*n:

return p

p = q+9-(q%10)

while not isprime(p):

p += 10 # Chai Wah Wu, Mar 08 2025

STATUS

approved

editing

A315644

Coordination sequence Gal.6.325.6 where Gal.u.t.v denotes the coordination sequence for a vertex of type v in tiling number t in the Galebach list of u-uniform tilings.
(history; published version)

#5 by Chai Wah Wu at Sat Mar 08 14:58:13 EST 2025

STATUS

editing

proposed

#4 by Chai Wah Wu at Sat Mar 08 14:58:07 EST 2025

FORMULA

Conjectures from Chai Wah Wu, Mar 08 2025: (Start)

a(n) = 2*a(n-1) - 2*a(n-2) + 2*a(n-3) - 2*a(n-4) + 2*a(n-5) - 2*a(n-6) + 2*a(n-7) - 2*a(n-8) + 2*a(n-9) - a(n-10) for n > 10.

G.f.: (x^10 + 4*x^9 + 2*x^8 + 2*x^7 + 4*x^6 + 4*x^4 + 2*x^3 + 2*x^2 + 4*x + 1)/((x - 1)^2*(x^4 - x^3 + x^2 - x + 1)*(x^4 + x^3 + x^2 + x + 1)). (End)

STATUS

approved

editing

A314838

Coordination sequence Gal.4.52.3 where Gal.u.t.v denotes the coordination sequence for a vertex of type v in tiling number t in the Galebach list of u-uniform tilings.
(history; published version)

#5 by Chai Wah Wu at Sat Mar 08 14:54:34 EST 2025

STATUS

editing

proposed

#4 by Chai Wah Wu at Sat Mar 08 14:53:51 EST 2025

FORMULA

Conjectures from Chai Wah Wu, Mar 08 2025: (Start)

a(n) = a(n-1) + a(n-7) - a(n-8) for n > 8.

G.f.: (x^8 + 4*x^7 + 4*x^6 + 5*x^5 + 4*x^4 + 5*x^3 + 4*x^2 + 4*x + 1)/(x^8 - x^7 - x + 1). (End)

STATUS

approved

editing

A243109

a(n) is the largest number smaller than n and having the same Hamming weight as n, or n if no such number exist.
(history; published version)

#34 by Chai Wah Wu at Sat Mar 08 11:26:07 EST 2025

STATUS

editing

proposed

#33 by Chai Wah Wu at Sat Mar 08 11:25:58 EST 2025

FORMULA

If n is even, then a(n) = XOR(n,OR(a,a/2)) where a = AND(-n,n+1). - Chai Wah Wu, Mar 08 2025

STATUS

approved

editing

A057168

Next larger integer with same binary weight (number of 1 bits) as n.
(history; published version)

#54 by Chai Wah Wu at Sat Mar 08 11:25:15 EST 2025

STATUS

editing

proposed