A276729 -id:A276729 - cp's OEIS frontend

A257629 Duplicate of A276729.

1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 3

Offset: 0

Giovanni Teofilatto, Jul 12 2015

dead

			a(10344) = 4 because 4 of the digits of 10344 (1, 0, 4 and 4) are nonprime.

Cf. A055642 (number of digits), A193238 (number of prime digits), A046034.

a[n_] := Length@ Intersection[ IntegerDigits[n], {0, 1, 4, 6, 8, 9}]; a/@ Range[0, 90] (* Giovanni Resta, Jul 14 2015 *)
Table[Count[IntegerDigits[n],?(!PrimeQ[#]&)],{n,0,100}] (* _Harvey P. Dale, Jan 16 2017 *)

a(n) = A055642(n) - A193238(n). - Michel Marcus, Jul 14 2015

Corrected and extended by Giovanni Resta, Jul 14 2015

Corrected and extended by Harvey P. Dale, Jan 16 2017

A342992 Smallest k such that k*n contains only prime digits, or 0 if no such k exists.

Original entry on oeis.org

2, 1, 1, 8, 1, 12, 1, 4, 3, 0, 2, 6, 4, 18, 5, 2, 15, 4, 3, 0, 12, 1, 1, 3, 1, 2, 1, 9, 8, 0, 12, 1, 1, 8, 1, 2, 1, 14, 7, 0, 13, 6, 54, 8, 5, 7, 5, 49, 15, 0, 5, 1, 1, 43, 1, 42, 1, 4, 43, 0, 12, 6, 4, 43, 5, 42, 5, 4, 8, 0, 5, 1, 1, 3, 1, 7, 1, 74, 3, 0, 93

Offset: 1

Metin Sariyar, Apr 13 2021

a(n) is 0 when n is divisible by 10, but when a(n) = 0, n is not always divisible by 10. For example, for n = 625, 1875, 3125, 4375, ... a(n) = 0 because no such k has been found yet for these numbers.
Conjecture: a(n) > 0 for all n that are not divisible by 5.
a(625*k) = 0 for k > 0 as the last four digits of (625*k), i.e., (625*k) mod 10000 always contains a nonprime digit. - David A. Corneth, Apr 21 2021

			a(4) = 8 because 8 is the smallest number k such that 8*4 = 32 contains only prime digits.

David A. Corneth, Table of n, a(n) for n = 1..10000
Chris K. Caldwell and G. L. Honaker, Jr., Prime Curios! 56479

Cf. A046034, A227922, A276729, A300289.

a(n) = if ((n % 10) && (n % 625), my(k=1); while (#select(x->!isprime(x), digits(k*n)), k++); k, 0); \\ Michel Marcus, Apr 21 2021

cp's OEIS Frontend

A257629 Duplicate of A276729.

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