A227306
Numbers k that divide sigma(k) + sigma(k-1).
Original entry on oeis.org
2, 6, 34, 50, 216, 236, 262, 386, 898, 924, 945, 1456, 2380, 5356, 6468, 6624, 8362, 14100, 23496, 26938, 46594, 80876, 196344, 212796, 1661136, 4070200, 4160920, 4626700, 5244548, 5462384, 17062316, 60464628, 217408416, 248621604, 262792908, 265371336, 323987588
Offset: 1
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With[{nn=324*10^6},Select[Thread[{Total/@Partition[DivisorSigma[ 1,Range[ nn]],2,1],Range[ 2,nn]}],Divisible[#[[1]],#[[2]]]&][[All,2]]] (* Harvey P. Dale, May 29 2020 *)
A346140
Numbers m such that there exist positive integers i <= m and j >= m such that m = Sum_{k=i..j} A001065(k), where A001065(k) = sum of the proper divisors of k, and i and j do not both equal m.
Original entry on oeis.org
2, 4, 5, 7, 8, 16, 29, 32, 39, 121, 128, 256, 279, 469, 1299, 3477, 7299, 7525, 8192, 13969, 19262, 19909, 26739, 31493, 54722, 65536, 99381, 131072, 357699, 524288, 13204262, 20742483, 33550337, 72873362
Offset: 1
2 is a term as A001065(2) = 1, A001065(3) = 1, and 1 + 1 = 2.
5 is a term as A001065(3) = 1, A001065(4) = 3, A001065(5) = 1, and 1 + 3 + 1 = 5.
29 is a term as A001065(28) = 28, A001065(29) = 1, and 28 + 1 = 29. This is an example of a prime number one more than a perfect number, thus it will appear in the sequence.
121 is a term as A001065(121) = 12, A001065(122) = 64, A001065(123) = 45, and 12 + 64 + 45 = 121.
19262 is a term as A001065(19261) = 3203, A001065(19262) = 9634, A001065(19263) = 6425, and 3203 + 9634 + 6425 = 19262. This is the first term that requires i < m and j > m.
Showing 1-2 of 2 results.
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