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%I #12 Mar 17 2023 11:21:56
%S 0,1,3,6,10,66,105,120,153,190,210,231,300,351,406,465,630,703,741,
%T 780,820,903,990,1035,1081,1326,1540,1770,1830,2016,2080,2556,2701,
%U 2850,3003,3081,3160,3240,3403,3570,4005,4095,4560,4950,5050,5460,5671,6105
%N Triangular numbers with product of digits also a triangular number.
%e 153 is a triangular number and the product of digits 15 is also a triangular number.
%p q:= n-> (l-> issqr(1+8*mul(i,i=l)))(convert(n, base, 10)):
%p select(q, [seq(i*(i+1)/2, i=0..110)])[]; # _Alois P. Heinz_, Mar 17 2023
%o (Magma) [t: n in [0..110] | IsSquare(8*p+1) where p is &*Intseq(t) where t is (n*(n+1) div 2)]; // _Bruno Berselli_, Jun 30 2011
%o (PARI) isok(k) = ispolygonal(k, 3) && ispolygonal(vecprod(digits(k)), 3); \\ _Michel Marcus_, Mar 17 2023
%Y Cf. A000217.
%K nonn,base,easy
%O 1,3
%A _Amarnath Murthy_, May 02 2001
%E More terms from _Erich Friedman_, May 08 2001
%E Offset 1 from _Michel Marcus_, Mar 17 2023
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