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A265835 Numbers n such that A015128(n)/2 is prime. 7
2, 4, 16, 36, 400, 1296, 1521, 52441 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Next term, if it exists, is greater than 4000000. - Vaclav Kotesovec, updated Apr 12 2017

The values of a(n) are the squares of these integers for 1 < n < 9: 2, 4, 6, 20, 36, 39, 229. Squares also appear in the sequence of numbers k such that A015128(k)/2 is semiprime. - Altug Alkan, Dec 16 2015

LINKS

Table of n, a(n) for n=1..8.

EXAMPLE

4 is a term because A015128(4)/2 = 14/2 = 7 is prime.

MATHEMATICA

Select[Range[2000], PrimeQ[Sum[PartitionsP[#-k]*PartitionsQ[k], {k, 0, #}]/2] &]

PROG

(PARI) a015128(n) = polcoeff(exp(sum(m=1, n\2+1, 2*x^(2*m-1)/(1-x^(2*m-1)+x*O(x^n))/(2*m-1))), n);

for(n=1, 1e3, if(ispseudoprime(a015128(n)/2), print1(n, ", "))) \\ Altug Alkan, Dec 16 2015

CROSSREFS

Cf. A014968, A015128, A035359, A046063, A299961.

Sequence in context: A074411 A189838 A247219 * A185074 A000216 A110998

Adjacent sequences:  A265832 A265833 A265834 * A265836 A265837 A265838

KEYWORD

nonn,more,hard

AUTHOR

Vaclav Kotesovec, Dec 16 2015

STATUS

approved

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Last modified January 26 16:58 EST 2020. Contains 331280 sequences. (Running on oeis4.)