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A355549
Number of positive integers k with 1 < k < n such that n occurs in the Reverse-and-Multiply trajectory of k.
1
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
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 A374017 A373974
KEYWORD
nonn,base
AUTHOR
Felix Fröhlich, Jul 06 2022
STATUS
approved