A117710 Pentagonal numbers for which the product of the digits is also a pentagonal number.

0, 1, 5, 51, 70, 210, 330, 590, 715, 1001, 1080, 1162, 1520, 1820, 2035, 2380, 2501, 3015, 3290, 3725, 4030, 4510, 5017, 5370, 6112, 6305, 6501, 6700, 6902, 7107, 7740, 8400, 9087, 9560, 9801, 10045, 10292, 10542, 10795, 11051, 11310, 11572, 12105

Offset: 0

Author

Luc Stevens (lms022(AT)yahoo.com), Apr 13 2006

Keywords

• base
• nonn

Examples

			715 is in the sequence because it is a pentagonal number and the product of its digits 7*1*5=35 is also a pentagonal number.
		

Crossrefs

Cf. A000326, A061380.

Programs

Mathematica

pn=Table[n (3 n - 1)/2, {n, 0, 90}] ;Select[pn,MemberQ[pn,Times@@IntegerDigits[#]]&] (* James C. McMahon, Sep 25 2024 *)