The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A139268

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A139268

Twice nonagonal numbers (or twice 9-gonal numbers): a(n) = n*(7*n-5).
(history; published version)

#40 by Alois P. Heinz at Fri Dec 27 21:03:37 EST 2024

STATUS

proposed

approved

#39 by Elmo R. Oliveira at Fri Dec 27 20:40:15 EST 2024

STATUS

editing

proposed

#38 by Elmo R. Oliveira at Fri Dec 27 20:40:02 EST 2024

CROSSREFS

Cf. A051868, A001106, A051868.

STATUS

proposed

editing

#37 by Elmo R. Oliveira at Fri Dec 27 20:32:21 EST 2024

STATUS

editing

proposed

#36 by Elmo R. Oliveira at Fri Dec 27 20:25:54 EST 2024

FORMULA

From Elmo R. Oliveira, Dec 27 2024: (Start)

E.g.f.: exp(x)*x*(2 + 7*x).

a(n) = n + A051868(n).

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 2. (End)

CROSSREFS

Cf. A051868, A001106.

Cf. numbers of the form n*(n*k - k + 4)/2 listed in A226488 (this sequence is the case k=14). - Bruno Berselli, Jun 10 2013

STATUS

approved

editing

#35 by Hugo Pfoertner at Fri Sep 27 02:53:36 EDT 2024

STATUS

reviewed

approved

#34 by Joerg Arndt at Fri Sep 27 02:00:49 EDT 2024

STATUS

proposed

reviewed

#33 by Michel Marcus at Fri Sep 27 02:00:22 EDT 2024

STATUS

editing

proposed

#32 by Michel Marcus at Fri Sep 27 02:00:16 EDT 2024

FORMULA

a(n) = 2*A001106(n)*2 = 7*n^2 - 5*n = n*(7*n-5).

STATUS

proposed

editing

#31 by Jason Yuen at Fri Sep 27 00:09:23 EDT 2024

STATUS

editing

proposed