A349251 a(n) is the integer reached after repeated application of the map x->A349194(x) or -1 if this process does not terminate.
1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 4, 6, 8, 1, 3, 5, 7, 9, 4, 8, 9, 3, 6, 9, 6, 3, 9, 9, 9, 9, 7, 4, 3, 4, 6, 9, 7, 6, 48, 3, 5, 9, 3, 7, 9, 5, 5, 9, 9, 3, 9, 3, 48, 9, 9, 9, 9, 6, 9, 9, 3, 5, 9, 3, 9, 9, 9, 9, 6, 8, 9, 9, 9, 9, 9, 5, 8, 9, 9, 7, 9
Offset: 1
Examples
For n=19, A349194(19) = 10 and A349194(10) = 1 and 1 is a fixed point of A349194 (see A349190), so a(19)=1.
Links
- Michel Marcus, Table of n, a(n) for n = 1..378
Programs
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Mathematica
f[n_] := Times @@ Accumulate @ IntegerDigits[n]; a[n_, itermax_] := Module[{m = FixedPoint[f, n, itermax]}, If[f[m] == m, m, 0]]; itermax = 100; Table[a[k, itermax], {k, 1, 100}] (* returns 0 if the number of iterations exceeds itermax, Amiram Eldar, Nov 12 2021 *) -
PARI
f(n) = my(d=digits(n)); prod(i=1, #d, sum(j=1, i, d[j])); \\ A349194 a(n) = {my(nb=0); while (1, my(m=f(n)); nb++; if (m==n, return (m)); if (nb > 100, return (0)); n = m;);}
Comments