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

Author

Olivier Gérard, Mar 05 2020

Keywords

• nonn

Examples

			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.
		

Crossrefs

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

Programs

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