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.

A364659 Numbers k such that sigma(k) < sigma(k+1) < sigma(k+2).

Original entry on oeis.org

1, 2, 61, 62, 73, 74, 133, 134, 145, 146, 193, 194, 253, 254, 313, 397, 398, 403, 457, 458, 481, 482, 493, 494, 523, 553, 554, 565, 566, 613, 614, 625, 626, 661, 662, 673, 674, 691, 733, 734, 757, 758, 763, 793, 794, 817, 818, 853, 854, 913, 914, 943, 973, 974, 997, 998
Offset: 1

Views

Author

Seiichi Manyama, Aug 01 2023

Keywords

Links

Crossrefs

Cf. A053224, A364657, A364662.

Programs

  • PARI
    isok(n) = sigma(n)

A364716 Numbers k such that d(k) < d(k+1) < d(k+2) < d(k+3), where d(n) is the number of divisors of n.

Original entry on oeis.org

61, 193, 277, 361, 397, 421, 457, 613, 757, 997, 1213, 1237, 1453, 1657, 1867, 1873, 1933, 2137, 2347, 2593, 2797, 2917, 3013, 3183, 3217, 3361, 3427, 3481, 3517, 3697, 3721, 3805, 4057, 4083, 4177, 4261, 4603, 4621, 4717, 4771, 4813, 4957, 5029, 5041, 5101, 5107, 5223
Offset: 1

Views

Author

Seiichi Manyama, Aug 04 2023

Keywords

Crossrefs

Cf. A000005, A075028, A364662, A364719.
Cf. A074775, A364715, A364717.

Programs

  • PARI
    isok(n) = numdiv(n)

A359666 Integers k such that sigma(k) <= sigma(k+1) <= sigma(k+2) <= sigma(k+3), where sigma is the sum of divisors.

Original entry on oeis.org

1, 13, 61, 73, 133, 145, 193, 205, 253, 397, 457, 481, 493, 553, 565, 613, 625, 661, 673, 733, 757, 793, 817, 853, 913, 973, 997, 1033, 1093, 1213, 1237, 1285, 1321, 1333, 1453, 1513, 1537, 1633, 1645, 1657, 1681, 1813, 1825, 1873, 1933, 2077, 2113, 2173, 2233, 2245, 2293, 2413, 2497
Offset: 1

Views

Author

Alexandru Petrescu, Feb 28 2023

Keywords

Examples

			73 is a term because sigma(73)=74 <= sigma(74)=114 <= sigma(75)=124 <= sigma(76)=140.

Links

Crossrefs

Cf. A000203, A053224, A323726, A364662.

Programs

  • Mathematica
    Position[OrderedQ /@ Partition[DivisorSigma[1, Range[2500]], 4, 1], True] // Flatten (* Amiram Eldar, Feb 28 2023 *)
  • PARI
    isok(n)=sigma(n)<=sigma(n+1) && sigma(n+1)<=sigma(n+2) && sigma(n+2)<=sigma(n+3)

A364704 Smallest initial number k of n consecutive numbers satisfying sigma(k) < sigma(k+1) < ... < sigma(k+n-1).

Original entry on oeis.org

1, 1, 1, 1, 36721681, 36721681
Offset: 1

Views

Author

Seiichi Manyama, Aug 03 2023

Keywords

Comments

a(7) > 5*10^10. (Calculated using the b-file in A028965.)

Crossrefs

Cf. A000203, A075028, A285893, A364680.
Cf. A028965, A053224, A364659, A364662.

Programs

  • PARI
    b(n) = my(k=n); while(sigma(k)
Showing 1-4 of 4 results.

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

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