A381510 - OEIS

A381510

Smaller of two consecutive primes p and q, both ending with 7, such that q - p = 10n, or -1 if no such primes exist.

337, 887, 4297, 33247, 31907, 124367, 218287, 1122287, 1964987, 1313467, 1468277, 7160227, 5518687, 16525757, 13626257, 71880637, 27915737, 17051707, 394059907, 566348087, 252314747, 472865287, 1289694257, 633418787, 1588640437, 944192807, 1391048047, 7059848287

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..28.

EXAMPLE

a(1) = 337, because 337 and 337 + 10 = 347 are two consecutive primes with the same last digit 9 and no smaller p has this property.

PROG

(PARI) a(n) = my(p=7); while (!isprime(p) || ((nextprime(p+1)-p) != 10*n), p+=10); p; \\ Michel Marcus, Feb 25 2025

CROSSREFS

Cf. A101232, A140791, A380785, A381372.

Sequence in context: A214492 A157999 A152853 * A142830 A160069 A201852

Adjacent sequences: A381499 A381500 A381502 * A381511 A381514 A381515

KEYWORD

nonn,base,new

AUTHOR

Jean-Marc Rebert, Feb 25 2025

STATUS

approved