A355550 a(n) is the smallest number k such that k occurs in the Reverse-and-Multiply trajectories of exactly n positive integers less than k.

0, 4, 16, 1300, 976, 40300, 662704, 12251200

Offset: 0

Author

Felix Fröhlich, Jul 06 2022

Keywords

• nonn
• base
• hard
• more

Comments

Smallest k such that A355549(k) = n.

Crossrefs

Cf. A355548, A355549.

Programs

PARI

revmult(n) = n*eval(concat(Vecrev(Str(n))))
a355549(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
a(n) = for(k=0, oo, if(a355549(k)==n, return(k)))

Extensions

a(5)-a(7) from Jinyuan Wang, Jul 07 2022