OFFSET

1,1

COMMENTS

As A053392(n) can be either larger or smaller than n this sequence lists n when it is either a multiple or a divisor of A053392(n). In the majority of terms n is a multiple of A053392(n); the first case where n is a divisor is a(27) = 182, where A053392(182) = 910.

All numbers of the form n = k*10^t, with k,t>=1 are in the sequence, as are numbers n = 75*10^t, with t>=1. Also present are numbers of the form n = 444...445 which have A053392 values like 888...889, for which n = 5*A053392(n). Similarly numbers of the form n = 444...455, which have A053392 values like 888...8910, for which A053392(n) = 2*n. For numbers up to 10^10 the largest term which is not one of these forms is a(120) = 654653884, which divides A053392(654653884) = 11910118111612.

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..180 (first 137 terms from Scott R. Shannon)

EXAMPLE

CROSSREFS

KEYWORD

nonn,base

AUTHOR

Scott R. Shannon, Feb 24 2020

STATUS

approved