A333014 Numbers which can written in exactly four ways as a sum of two distinct nonzero pentagonal numbers.

13352, 18877, 45397, 49052, 52027, 53727, 62652, 64182, 73152, 74977, 76677, 79327, 80671, 85177, 87972, 88577, 90702, 91652, 93302, 96669, 98827, 101752, 106036, 106822, 109227, 109487, 116117, 118477, 125347, 133267, 135786, 138087, 138802, 140852, 141532, 144747, 145302, 145641, 147274, 148077, 148927

Offset

1,1

Links

Table of n, a(n) for n=1..41.

Example

13352 = P(52) + P(79) = P(29) + P(90) = P(17) + P(93) = P(10) + P(94), where P(n) is the n-th pentagonal number A000326.

Prog

(PARI) is(k) = sum(i=1, sqrt(1+12*k)\6, sqrt(1+24*k+12*i-36*i*i)%6==5) == 4; \\ Jinyuan Wang, Mar 06 2020

Crossrefs

Cf. A000326, A332988, A332989, A333011, A333012, A333013.

Sequence in context: A162423 A176465 A185503 * A205196 A235297 A252240

Adjacent sequences: A333011 A333012 A333013 * A333015 A333016 A333017

Keyword

nonn

Author

Olivier Gérard, Mar 05 2020

Status

approved