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A135244 Aliquot predecessors with the largest values. 3
0, 4, 9, 0, 25, 8, 49, 15, 14, 21, 121, 35, 169, 33, 26, 55, 289, 77, 361, 91, 38, 85, 529, 143, 46, 133, 28, 187, 841, 221, 961, 247, 62, 253, 24, 323, 1369, 217, 81, 391, 1681, 437, 1849, 403, 86, 493, 2209, 551, 94, 589, 0, 667, 2809, 713, 106, 703, 68, 697, 3481 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

Find each node's predecessors in aliquot sequences and choose the largest predecessor.

Climb the aliquot trees on shortest paths (see A135245 = Climb the aliquot trees on thickest branches).

The sequence starts at offset 2, since all primes satisfy sigma(n)-n = 1. - Michel Marcus, Nov 11 2014

LINKS

Ophir Spector, Table of n, a(n) for n = 2..150

W. Creyaufmueller, Aliquot sequences

J. O. M. Pedersen, Tables of Aliquot Cycles [Broken link]

J. O. M. Pedersen, Tables of Aliquot Cycles [Via Internet Archive Wayback-Machine]

J. O. M. Pedersen, Tables of Aliquot Cycles [Cached copy, pdf file only]

Eric Weisstein's World of Mathematics, Aliquot sequence

EXAMPLE

a(25) = 143 since 25 has 3 predecessors (95,119,143), 143 being the largest. a(5) = 0 since it has no predecessors (see Untouchables - A005114).

PROG

(PARI) lista(nn) = {for (n=2, nn, k = (n-1)^2; while(k && (sigma(k)-k != n), k--); print1(k, ", "); ); } \\ Michel Marcus, Nov 11 2014

CROSSREFS

Cf. A001065, A005114, A125601, A135245, A057709, A057710, A063769, A080907, A121507, A037020, A126016.

Sequence in context: A272102 A056584 A135245 * A011514 A238261 A245238

Adjacent sequences:  A135241 A135242 A135243 * A135245 A135246 A135247

KEYWORD

nonn

AUTHOR

Ophir Spector (ospectoro(AT)yahoo.com), Nov 25 2007

EXTENSIONS

a(1)=0 removed and offset set to 2 by Michel Marcus, Nov 11 2014

STATUS

approved

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Last modified March 26 19:03 EDT 2019. Contains 321511 sequences. (Running on oeis4.)