A188665 Primes of the form n^2+number of divisors of n^2.

2, 7, 71, 109, 1321, 1453, 1621, 1951, 2719, 3373, 3853, 4639, 5791, 6427, 6733, 9619, 10837, 11699, 13933, 15391, 16927, 18517, 20173, 23743, 25633, 28927, 29599, 33151, 40813, 43291, 44959, 47533, 55711, 56671, 58579, 70783, 80671, 84127, 88813

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

a(n) = A188539(n)^2 + A000005(A188539(n)^2).

Example

a(5)=1321 because 36^2+A000005(36^2)=1321.

Maple

select(isprime, map(n -> n^2 + numtheory:-tau(n^2), [1, seq(i, i=2..1000, 2)])); # Robert Israel, Apr 11 2018

Mathematica

Select[Table[n^2+DivisorSigma[0, n^2], {n, 300}], PrimeQ] (* Harvey P. Dale, Oct 20 2016 *)

Crossrefs

Cf. A000005, A188539.

Sequence in context: A113866 A165978 A106917 * A198188 A230459 A267406

Adjacent sequences: A188662 A188663 A188664 * A188666 A188667 A188668

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 07 2011

Extensions

Edited by Robert Israel, Apr 11 2018

Status

approved