A172437 Indices of pentagonal pyramidal numbers which are the sum of two other such numbers: k such that A002411(k) = A002411(i)+A002411(j) for some i,j>0.

42, 82, 171, 411, 522, 886, 1042, 1066, 1183, 1341, 2596, 2842, 3480, 3831, 5012, 5316, 5360, 5786, 6219, 6650, 6924, 8406, 8666, 9408, 10707, 11735, 12590, 12891, 14422, 14646, 14826, 17351, 17702, 17757, 18882, 23210, 24108, 25127, 28175, 31980, 32400

Offset: 1

Author

M. F. Hasler, Nov 20 2010

Keywords

• nonn

Comments

The numbers themselves are listed in A172425. This answers a question posed in A133459.

Examples

			a(1)=42 because A002411(42) is the smallest term in that sequence which is the sum of two other (nonzero) terms of A002411.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..160

Crossrefs

Cf. A133459, A172425.

Programs

PARI

for(n=1,99999,for(m=1,n-1, isA002411(p(n)-p(m)) & !print1(n", ") & break)) /* needs isA002411() and p() */