A349251 - OEIS

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

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OFFSET

1,2

COMMENTS

Heuristics suggest that numbers n such that a(n) = -1 have density 1 and may be quite dense by 10^10. - Charles R Greathouse IV, Nov 15 2021

LINKS

Michel Marcus, Table of n, a(n) for n = 1..378

EXAMPLE

For n=19, A349194(19) = 10 and A349194(10) = 1 and 1 is a fixed point of A349194 (see A349190), so a(19)=1.

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 *)

PROG

(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; ); }

CROSSREFS

Cf. A349190, A349194.

Sequence in context: A128244 A010888 A177274 * A131650 A033930 A076314

Adjacent sequences: A349248 A349249 A349250 * A349252 A349253 A349254

KEYWORD

nonn,base

AUTHOR

Michel Marcus, Nov 12 2021

STATUS

approved