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 A234899 Record holders for lengths of ever-decreasing aliquot sequences. 2
 1, 2, 4, 9, 14, 16, 26, 46, 52, 166, 212, 1113, 2343, 4437, 5145, 8535, 10665, 18711, 33682, 64935, 114808, 187232, 228316, 304412, 464132, 556636, 623288, 1230284, 1319956, 1508504, 2897884, 3835556, 7487494, 9446906, 16871648, 22328212, 29668150, 29725184 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS If one looks at the lengths of uninterrupted decreasing aliquot sequences, the converse of A081705, one gets a sequence similar to A098008, except for perfect or abundant numbers, but also for numbers that encounter a perfect or abundant numbers in this process. The current sequence lists the deficient numbers yielding uninterrupted decreasing aliquot sequences that are longer than any previous ones (compare with A081699). Note that, so far, the lengths of the corresponding sequences are contiguous. Does it remain so for next terms? LINKS Amiram Eldar, Table of n, a(n) for n = 1..59 EXAMPLE The aliquot sequence starting at 2 decreases as follows 2->1->0 and is longer than the sequence starting at 1. Hence 2 is in the sequence. PROG (PARI) nbdecr(n) = {nb = 0; while (n && ((newn = sigma(n)-n)) < n, n = newn ; nb++); nb; } lista(nn) = {recab = 0; for (ni = 1, nn, ab = nbdecr(ni); if (ab > recab, recab = ab; print1(ni, ", ")); ); } CROSSREFS Cf. A081699, A081705, A098008. Sequence in context: A085901 A077224 A059447 * A190553 A270532 A281407 Adjacent sequences: A234896 A234897 A234898 * A234900 A234901 A234902 KEYWORD nonn AUTHOR Michel Marcus, Jan 01 2014 STATUS approved

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Last modified May 17 19:53 EDT 2024. Contains 372607 sequences. (Running on oeis4.)