A078240 -id:A078240 - cp's OEIS frontend

A078250 a(1) = 1, a(n) = smallest multiple of n using prime digits if n is composite else smallest multiple of n using composite digits, with a(n) = 0 if there are none.

1, 4, 6, 32, 40, 72, 49, 32, 27, 0, 44, 72, 468, 252, 75, 32, 68, 72, 494, 0, 252, 22, 46, 72, 25, 52, 27, 252, 406, 0, 496, 32, 33, 272, 35, 72, 444, 532, 273, 0, 984, 252, 86, 352, 225, 322, 94, 2352, 735, 0, 255, 52, 689, 2322, 55, 2352, 57, 232, 649, 0

Offset: 1

Amarnath Murthy, Nov 24 2002

Besides multiples of 10, 625 and its odd multiples have a(n)=0. Based on comment by Robert Israel in A078239. - Andrew Howroyd, Sep 17 2024

Andrew Howroyd, Table of n, a(n) for n = 1..10000

Cf. A074162, A078239, A078240.

a(n)={if(n%10==0||n%1250==625, 0, if(n==1, 1, my(S=Set([2, 3, 5, 7])); forstep(m=n, oo, n, my(d=digits(m)); if(0 == #if(isprime(n),select(t->t==1||setsearch(S, t), d), select(t->!setsearch(S,t),d)), return(m)))))} \\ Andrew Howroyd, Sep 17 2024

a(13) corrected and a(29) onwards from Andrew Howroyd, Sep 17 2024

A113591 Least multiple of composite(n), containing only composite digits (0,4,6,8,9).

Original entry on oeis.org

0, 4, 6, 8, 9, 40, 48, 84, 60, 48, 90, 40, 84, 44, 48, 400, 468, 486, 84, 60, 64, 66, 68, 490, 468, 494, 468, 40, 84, 44, 90, 46, 48, 49, 400, 408, 468, 486, 440, 448, 684, 406, 60, 496, 6048, 64, 4680, 66, 68, 69, 490, 648, 444, 600, 608, 4004, 468, 80, 486, 984, 84

Offset: 0

Amarnath Murthy, Nov 07 2005

The sequence A002808 is extended with A002808(0)=0 to define "composite" here. Every term occurs in A001744. - R. J. Mathar, Aug 28 2007

			a(7) = 84, composite (7) =14, term corresponding to 14 is 84.

Cf. A002808, A078240, A113590.

a(n) = A078240(A002808(n)) for n > 0. - Andrew Howroyd, Sep 17 2024

Corrected and extended by R. J. Mathar, Aug 28 2007

cp's OEIS Frontend

A078250 a(1) = 1, a(n) = smallest multiple of n using prime digits if n is composite else smallest multiple of n using composite digits, with a(n) = 0 if there are none.

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