A355549 Number of positive integers k with 1 < k < n such that n occurs in the Reverse-and-Multiply trajectory of k.

0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0

Offset

0,17

Links

Table of n, a(n) for n=0..86.

Prog

(PARI) revmult(n) = n*eval(concat(Vecrev(Str(n))))
a(n) = my(i=0); for(k=2, n-1, my(x=k); while(x < n, if(x==revmult(x), break, x=revmult(x))); if(x==n, i++)); i

Crossrefs

Cf. A355550.

Sequence in context: A072507 A004530 A368980 * A347438 A245196 A259362

Adjacent sequences: A355546 A355547 A355548 * A355550 A355551 A355552

Keyword

nonn,base

Author

Felix Fröhlich, Jul 06 2022

Status

approved