A117799 Icosagonal numbers for which the sum of the digits is also an icosagonal number.

0, 1, 7337, 12692, 19505, 37505, 61337, 75440, 146432, 240752, 326801, 358400, 620417, 708401, 802217, 851312, 1007345, 1062272, 1176500, 1235801, 1422452, 1622225, 1835120, 1909001, 2061137, 2219105, 2300276, 2728001, 4010672, 4803401, 5043017, 5165012, 7026032, 7315220, 7462001

Offset: 1

Author

Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006

Keywords

• nonn
• base

Examples

			7337 is in the sequence because (1) it is an icosagonal number and (2) the sum of the digits 7+3+3+7=20 is also an icosagonal number.
		

Crossrefs

Cf. A007953, A051872.

Programs

PARI

isok(n) = ispolygonal(n, 20) && ispolygonal(sumdigits(n), 20); \\ Michel Marcus, Feb 27 2014

Extensions

a(11) corrected by Georg Fischer, Mar 27 2024