cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A304745 Restricted growth sequence transform of A046523(A207901(n)).

Original entry on oeis.org

1, 2, 3, 2, 4, 5, 6, 7, 4, 5, 8, 9, 3, 10, 3, 2, 3, 10, 11, 10, 12, 13, 8, 9, 4, 5, 8, 9, 3, 10, 3, 2, 4, 9, 8, 5, 14, 15, 14, 16, 17, 18, 19, 18, 8, 13, 12, 9, 4, 9, 8, 5, 14, 15, 14, 16, 20, 21, 22, 21, 6, 5, 4, 7, 4, 9, 8, 5, 14, 15, 14, 16, 17, 18, 19, 18, 8, 13, 12, 9, 12, 23, 24, 13, 25, 26, 25, 27, 17, 18, 19, 18, 8, 13, 12, 9, 3, 10, 11, 10, 12, 13, 8
Offset: 0

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Author

Antti Karttunen, May 27 2018

Keywords

Comments

For all i, j: a(i) = a(j) => A005811(i) = A005811(j).

Crossrefs

Programs

  • PARI
    up_to_e = 17; \\ Good for computing up to n = (2^up_to_e)-1
    v050376 = vector(up_to_e);
    ispow2(n) = (n && !bitand(n,n-1));
    i = 0; for(n=1,oo,if(ispow2(isprimepower(n)), i++; v050376[i] = n); if(i == up_to_e,break));
    A050376(n) = v050376[n];
    A052330(n) = { my(p=1,i=1); while(n>0, if(n%2, p *= A050376(i)); i++; n >>= 1); (p); };
    A003188(n) = bitxor(n, n>>1);
    A207901(n) = A052330(A003188(n));
    A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); };  \\ From A046523
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    v304745 = rgs_transform(vector(65538,n,A046523(A207901(n-1))));
    A304745(n) = v304745[1+n];