A075017 - OEIS

A075017

Smallest k such that the concatenation k, k+1,k+2,k+3 is divisible by n; or 0 if no such number exists.

1, 1, 3, 3, 2, 3, 2, 3, 3, 7, 8, 3, 7, 17, 12, 3, 5, 3, 19, 17, 24, 15, 17, 3, 22, 7, 3, 17, 17, 27, 6, 3, 15, 5, 2, 3, 9, 19, 15, 17, 15, 45, 44, 37, 12, 17, 39, 3, 45, 47, 21, 41, 52, 3, 37, 17, 57, 17, 62, 57, 53, 53, 66, 3, 7, 15, 2, 21, 63, 17, 12, 3, 6, 9, 72

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..75.

EXAMPLE

a(7) = 2 as 7 divides 2345.

PROG

(PARI) isok(k, n) = my(v = Str(k)); for (j=1, 3, v = concat(v, Str(k+j))); (eval(v) % n) == 0;

a(n) = my(k=1); while (!isok(k, n), k++); k; \\ Michel Marcus, Jan 21 2017

CROSSREFS

Cf. A075113, A075114, A075115, A075116.