A078239 -id:A078239 - cp's OEIS frontend

A078240 a(n) = smallest multiple of n using only composite digits (0,4,6,8,9).

4, 4, 6, 4, 40, 6, 49, 8, 9, 40, 44, 48, 468, 84, 60, 48, 68, 90, 494, 40, 84, 44, 46, 48, 400, 468, 486, 84, 406, 60, 496, 64, 66, 68, 490, 468, 444, 494, 468, 40, 984, 84, 86, 44, 90, 46, 94, 48, 49, 400, 408, 468, 689, 486, 440, 448, 684, 406, 649, 60

Offset: 1

Amarnath Murthy, Nov 23 2002

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

Cf. A001744, A078239, A078250.

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

Corrected and extended by Andrew Howroyd, Sep 17 2024

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.

Original entry on oeis.org

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

cp's OEIS Frontend

A078240 a(n) = smallest multiple of n using only composite digits (0,4,6,8,9).

Views

Author

Keywords

Links

Crossrefs

Programs

PARI

Extensions