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.

Showing 1-4 of 4 results.

A318735 Positive records in A318734.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 16, 17, 21, 23, 25, 30, 31, 32, 34, 39, 45, 47, 48, 51, 52, 56, 60, 62, 71, 76, 78, 83, 84, 88, 91, 103, 108, 119, 127, 129, 132, 142, 143, 151, 166, 168, 171, 178, 181, 183, 189, 197, 215, 237, 241, 244, 266, 270, 274
Offset: 1

Views

Author

Hugo Pfoertner, Sep 05 2018

Keywords

Links

Crossrefs

Cf. A000005, A099774, A318734, A318736, A318737, A318738.

Programs

  • PARI
    s=0;smax=0;j=-1;forstep(k=1,20000000,2,j=-j;s=s+j*numdiv(k);if(s>smax,smax=s;print1(s,", ")))

A318736 Absolute value of negative records in A318734.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 14, 15, 19, 21, 22, 23, 25, 30, 32, 36, 40, 42, 44, 46, 50, 53, 55, 56, 57, 59, 65, 67, 69, 73, 79, 87, 96, 98, 100, 104, 108, 110, 113, 115, 118, 122, 126, 134, 139, 151, 161, 167, 169, 172, 178, 180, 182
Offset: 1

Views

Author

Hugo Pfoertner, Sep 05 2018

Keywords

Comments

1

Links

Crossrefs

Cf. A000005, A099774, A318734, A318735, A318737, A318738.

Programs

  • PARI
    s=0;j=-1;smin=0;forstep(k=1,5000000,2,j=-j;s=s+j*numdiv(k);if(s

A318737 Numbers n=2*k-1 where Sum_{j=1..k} (-1)^(j+1) * d(2*j-1) achieves a new record, with d(n) = number of divisors of n (A000005).

Original entry on oeis.org

1, 9, 25, 49, 85, 133, 169, 225, 445, 845, 973, 1125, 2205, 2209, 2469, 2829, 7929, 9429, 9945, 23569, 24073, 24645, 26145, 40425, 68153, 71289, 72413, 89517, 112233, 112245, 128973, 162405, 162409, 162429, 297073, 477489, 477493, 502713, 561253
Offset: 1

Views

Author

Hugo Pfoertner, Sep 05 2018

Keywords

Examples

			a(2) = 9, because s = d(1)-d(3)+d(5)-d(7)+d(9) = 1-2+2-2+3 = 2 exceeds d(1)=1, d(1)-d(3)=-1, d(1)-d(3)+d(5)=1, d(1)-d(3)+d(5)-d(7)=-1.

Links

Crossrefs

Cf. A000005, A099774, A318734, A318735, A318736, A318738.

Programs

  • PARI
    s=0;smax=0;j=-1;forstep(k=1,600000,2,j=-j;s=s+j*numdiv(k);if(s>smax,smax=s;print1(k,", ")))

A318738 Numbers n=2*k-1 where Sum_{j=1..k} (-1)^(j+1) * d(2*j-1) achieves a new negative record, with d(n) = number of divisors of n (A000005).

Original entry on oeis.org

3, 15, 39, 63, 99, 259, 319, 403, 675, 679, 943, 1615, 1779, 2919, 4899, 5775, 7399, 7407, 13475, 13479, 25635, 29835, 29839, 44955, 78463, 78475, 108927, 108931, 126819, 136959, 136975, 136983, 244875, 244879, 256355, 276675, 276687, 457275, 530139
Offset: 1

Views

Author

Hugo Pfoertner, Sep 08 2018

Keywords

Examples

			a(1) = 3, because s = d(1)-d(3) = 1-2 = -1 is the first negative record.
a(2) = 15, because s = d(1)-d(3)+d(5)-d(7)+d(9)-d(11)+d(13)-d(15) =
1-2+2-2+3-2+2-4 = -2 is the first sum less than -1.

Links

Crossrefs

Cf. A000005, A099774, A318734, A318735, A318736, A318737.

Programs

  • PARI
    s=0;j=-1;smin=0;forstep(k=1,600000,2,j=-j;s=s+j*numdiv(k);if(s
Showing 1-4 of 4 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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