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A188665
Primes of the form n^2+number of divisors of n^2.
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
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
Sequence in context: A113866 A165978 A106917 * A198188 A230459 A267406
KEYWORD
nonn
AUTHOR
EXTENSIONS
Edited by Robert Israel, Apr 11 2018
STATUS
approved