A279091 - OEIS

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A279091

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

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

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OFFSET

1,2

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?

LINKS

Michel Marcus, Table of n, a(n) for n = 1..77

EXAMPLE

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.

PROG

(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