A056907 - OEIS

A056907

Numbers k such that 36*k^2 + 12*k + 5 is prime (sorted by absolute values with negatives before positives).

0, -1, 1, 2, -3, -6, 6, -8, -11, 11, 12, 14, -16, 16, 17, 19, -21, -23, -26, 27, -28, 32, -34, -36, 36, -39, 39, -41, 42, 44, -46, 46, -48, -49, 51, 52, -53, -58, 62, 64, 67, -68, -71, 71, -76, 77, 79, 81, -84, -89, 91, 96, -99, -101, 101, 102, -104, -111, 111, -113

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OFFSET

0,4

COMMENTS

36*k^2 + 12*k + 5 = (6*k+1)^2 + 4, which is four more than a square. Except for a(0), a(n) is never a multiple of 5.

LINKS

Table of n, a(n) for n=0..59.

EXAMPLE

a(3)=2 since 36*2^2 + 12*2 + 5 = 173 which is prime (as well as being four more than a square).

CROSSREFS

This sequence and formula, together with A056908 and its formula, generate all primes of the form k^2+4, i.e., A005473. Except for the first term, this sequence is a subsequence of A047201. Cf. A056900, A056902, A056904, A056906.

Sequence in context: A080235 A198516 A187326 * A039799 A185423 A144583

Adjacent sequences: A056904 A056905 A056906 * A056908 A056909 A056910

KEYWORD

sign

AUTHOR

Henry Bottomley, Jul 07 2000

STATUS

approved