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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A279091 Numbers k for which sigma(k) - 4k exceeds sigma(j) - 4j for all j < k.

Original entry on oeis.org

1, 27720, 50400, 55440, 83160, 110880, 166320, 221760, 277200, 332640, 360360, 443520, 471240, 498960, 554400, 655200, 665280, 720720, 942480, 1053360, 1081080, 1330560, 1413720, 1441440, 1663200, 1801800, 1884960, 2106720, 2162160, 2827440, 2882880, 3326400
Offset: 1

Views

Author

Jon E. Schoenfield, Jan 30 2017

Keywords

Comments

Does lcm(1..10) = 2520 divide a(n) for all n > 1?
Does lcm(1..11) = 27720 divide a(n) for all n except 1, 3, and 16?

Examples

			50400 is in the sequence because sigma(50400) - 4*50400 = 203112 - 201600 = 1512, and no k < 50400 has a value of sigma(k) - 4k this large.

Links

Crossrefs

Cf. A034090, A140522, A279088: with 1, 2 and 3 instead of 4.

Programs

  • PARI
    lista(nn) = {m = -oo; k = 0; for (n=1, nn, if ((nm = (sigma(n) - 4*n)) > m, k++; print1(n, ", "); m = nm););} \\ Michel Marcus, Nov 02 2017
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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