A214516 Differences between the numbers n such that n^2 + 1 is prime.

1, 2, 2, 4, 4, 2, 4, 4, 2, 10, 4, 14, 2, 10, 8, 10, 6, 4, 16, 6, 4, 4, 2, 4, 4, 12, 4, 6, 4, 10, 6, 4, 4, 20, 2, 4, 14, 6, 6, 4, 10, 6, 4, 4, 6, 10, 4, 16, 6, 8, 12, 14, 10, 34, 2, 10, 4, 6, 14, 10, 6, 4, 4, 20, 2, 4, 4, 16, 6, 40, 8, 12, 14, 6, 8, 10, 40, 2

Offset: 1

Author

T. D. Noe, Aug 06 2012

Keywords

• nonn

Comments

Sequence A005574 has the values of n. This sequence is the first differences of A005574. Note that a(1) is the only odd value.

Links

• T. D. Noe, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002496 (primes of the form 1+n^2), A005574 (values of n).

Programs

Mathematica

Differences[Select[Range[100], PrimeQ[1 + #^2] &, 101]]

Formula

a(n) = 2*A214517(n) for n > 1.