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
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..10000
Programs
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PARI
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
Extensions
a(13) corrected and a(29) onwards from Andrew Howroyd, Sep 17 2024
Comments