OFFSET
1,2
EXAMPLE
a(5) = 79 because 7*1! + 9*2! = 5^2.
MATHEMATICA
PROG
(PARI) f(n) = my(d=digits(n)); sum(k=1, #d, d[k]*k!);
a(n) = my(k=1); while (f(k) != n^2, k++); k; \\ Michel Marcus, Jul 11 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Michel Lagneau, Oct 21 2011
STATUS
approved