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.

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A286450 Restricted growth sequence computed for A252750.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 6, 3, 2, 7, 8, 1, 9, 10, 11, 12, 7, 13, 14, 5, 15, 16, 17, 14, 18, 19, 20, 21, 22, 23, 24, 12, 25, 1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 1, 5, 56, 31, 57, 58, 59, 7, 60, 61, 62, 17, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81
Offset: 1

Views

Author

Antti Karttunen, May 13 2017

Keywords

Crossrefs

Programs

  • PARI
    rgs_transform(invec) = { my(occurrences = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(occurrences,invec[i]), my(pp = mapget(occurrences, invec[i])); outvec[i] = outvec[pp] , mapput(occurrences,invec[i],i); outvec[i] = u; u++ )); outvec; };
    write_to_bfile(start_offset,vec,bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }
    A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ This function from Michel Marcus
    A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); t }; \\ Modified from code of M. F. Hasler
    A252750(n) = (A003961(A005940(n+1)) - (2 * A005940(n+1)));
    write_to_bfile(1,rgs_transform(vector(10000,n,A252750(n))),"b286450.txt");

A293438 Product of deficiencies of proper divisors of n.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 2, 4, 1, 0, 1, 6, 8, 1, 1, 0, 1, 8, 12, 10, 1, 0, 4, 12, 10, 24, 1, 0, 1, 1, 20, 16, 24, 0, 1, 18, 24, -16, 1, 0, 1, 80, 240, 22, 1, 0, 6, 152, 32, 120, 1, 0, 40, 0, 36, 28, 1, 0, 1, 30, 600, 1, 48, 0, 1, 224, 44, 4224, 1, 0, 1, 36, 912, 288, 60, 0, 1, 160, 140, 40, 1, 0, 64, 42, 56, 320, 1, 0, 72, 440, 60, 46, 72
Offset: 1

Views

Author

Antti Karttunen, Dec 01 2017

Keywords

Comments

There are only 643 negative values in range 1 .. 16384.

Examples

			The proper divisors of 15 are 1, 3, 5. Their deficiencies (A033879) are 1, 2, 4. Thus a(15) = 1*2*4 = 8.
The proper divisors of 18 are 1, 2, 3, 6, 9. Their deficiencies are 1, 1, 2, 0, 5, thus a(18) = 1*1*2*0*5 = 0.
The proper divisors of 40 are 1, 2, 4, 5, 8, 10, 20. Their deficiencies are 1, 1, 1, 4, 1, 2, -2, thus a(40) = 1 * 1 * 1 * 4 * 1 * 2 * -2 = -16.
		

Crossrefs

Programs

  • PARI
    A033879(n) = ((2*n)-sigma(n));
    A293438(n) = { my(m=1); fordiv(n,d,if(dA033879(d))); (m); };

Formula

a(n) = Product_{d|n, dA033879(d).
a(A000040(n)) = 1, a(A000079(n)) = 1.

A318309 Restricted growth sequence transform of A083254 (2*phi(n) - n).

Original entry on oeis.org

1, 2, 1, 2, 3, 4, 5, 2, 3, 4, 6, 7, 8, 4, 1, 2, 9, 10, 11, 7, 3, 4, 12, 13, 9, 4, 6, 7, 14, 15, 16, 2, 17, 4, 18, 19, 20, 4, 6, 13, 21, 22, 23, 7, 3, 4, 24, 25, 20, 26, 18, 7, 27, 22, 28, 13, 9, 4, 29, 30, 31, 4, 6, 2, 32, 33, 34, 7, 35, 36, 37, 38, 39, 4, 5, 7, 40, 41, 42, 25, 14, 4, 43, 44, 40, 4, 28, 13, 45, 46, 47, 7, 14, 4, 48, 49, 50, 15, 12, 51
Offset: 1

Views

Author

Antti Karttunen, Aug 26 2018

Keywords

Crossrefs

Programs

  • PARI
    up_to = 65537;
    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; };
    A083254(n) = (2*eulerphi(n)-n);
    v318309 = rgs_transform(vector(up_to,n,A083254(n)));
    A318309(n) = v318309[n];

A318308 Restricted growth sequence transform of A294898.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 4, 1, 4, 1, 5, 6, 7, 8, 2, 1, 9, 10, 11, 12, 5, 13, 14, 15, 16, 5, 17, 18, 19, 20, 21, 1, 16, 22, 23, 24, 25, 26, 14, 27, 28, 29, 30, 8, 31, 16, 32, 33, 30, 34, 35, 4, 36, 20, 25, 37, 38, 39, 40, 41, 42, 43, 16, 1, 44, 15, 45, 31, 46, 47, 48, 49, 50, 51, 39, 7, 52, 20, 53, 54, 30, 55, 56, 57, 58, 59, 60, 47, 61, 62, 63, 22, 40, 46, 64
Offset: 1

Views

Author

Antti Karttunen, Aug 26 2018

Keywords

Crossrefs

Programs

  • PARI
    up_to = 65537;
    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; };
    A294898(n) = (2*n - sigma(n) - hammingweight(n));
    v318308 = rgs_transform(vector(up_to,n,A294898(n)));
    A318308(n) = v318308[n];
Previous Showing 11-14 of 14 results.