A261525 a(n) = smallest m such that A031131(m) = 2*n.

2, 3, 9, 8, 15, 23, 47, 29, 66, 114, 46, 220, 188, 258, 640, 375, 480, 589, 216, 326, 367, 1006, 738, 1183, 1985, 1847, 1662, 2224, 3731, 3861, 3561, 2699, 3792, 4521, 2225, 12541, 3384, 12761, 3385, 4058, 10228, 15747, 15927, 14357, 18280, 19025, 14123

Offset

2,1

Comments

A031131(a(n)) = 2*n and A031131(m) != 2*n for m < a(n);

A046931(n) = A000040(a(n)+1);

a(n)-th and (a(n)+2)-nd primes are the first pair that differ by 2*n;

conjecture: sequence is defined for all n > 1.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 2..100

Prog

(Haskell)
a261525 = (+ 1) . fromJust . (`elemIndex` a031131_list) . (* 2)

Crossrefs

Cf. A031131, A038664, A046931.

Sequence in context: A246825 A086565 A008291 * A122665 A133066 A337998

Adjacent sequences: A261522 A261523 A261524 * A261526 A261527 A261528

Keyword

nonn

Author

Reinhard Zumkeller, Aug 23 2015

Status

approved