A166119 a(n) = A165966(n)/12.

3, 10, 23, 25, 213, 270, 455, 688, 1060, 1953, 2233, 2915, 3468, 3838, 4718, 4945, 8645, 10230, 11638, 12308, 13090, 15428, 16250, 19295, 23095, 27778, 29435, 32230, 33488, 43053, 50830, 71668, 83485, 86460, 89365, 96330, 104610, 106600, 127823

Offset

1,1

Comments

The only known primes in the sequence are 3, 23.

Links

Table of n, a(n) for n=1..39.

Formula

a(n) = (A086816(n) + 1)/6. - Alois P. Heinz, Sep 18 2024

Prog

(PARI) lista(nn) = {for (n = 1, nn, trg = n*(n+1)/2; if (!(trg % 2) && isprime(trg/2-1) && isprime(trg/2+1), print1(trg/12, ", ")); ); } \\ Michel Marcus, Oct 16 2013

Crossrefs

Cf. A000217, A001359, A086816, A105174, A111163, A165966.

Sequence in context: A027164 A292921 A270470 * A041403 A077126 A172113

Adjacent sequences: A166116 A166117 A166118 * A166120 A166121 A166122

Keyword

nonn,changed

Author

Zak Seidov, Oct 07 2009

Status

approved