The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A101260 Numbers n whose abundance is 56. 2
 84, 140, 224, 308, 364, 476, 532, 644, 812, 868, 1036, 1148, 1204, 1316, 1372, 1484, 1652, 1708, 1876, 1988, 2044, 2212, 2324, 2492, 2716, 2828, 2884, 2996, 3052, 3164, 3556, 3668, 3836, 3892, 4172, 4228, 4396, 4544, 4564, 4676, 4844, 5012, 5068, 5348 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If n is of the form p*28, where p is a prime distinct from 2 or 7 then n is in this sequence, note that 28 is a perfect number. The terms in the sequence but not divisible by 28 are 4544, 9272, 14552, 25472, 74992, 495104... - Enrique Pérez Herrero, Apr 15 2012 If p=2^k-57 is prime (cf. A165778), then 2^(k-1)*p is in the sequence: For the first such k=6,7,8,10,16,19,22,28,..., this yields 224, 4544, 25472, 495104, 2145615872, 137424011264, 8795973484544, 36028789368553472, ... - M. F. Hasler, Apr 15 2012 LINKS Enrique Pérez Herrero, Table of n, a(n) for n = 1..3000 F. Firoozbakht and M. F. Hasler, Variations on Euclid's formula for Perfect Numbers, JIS 13 (2010) #10.3.1. EXAMPLE 84 is a term of the sequence because 2*2*3*7 = 84 and 84 - 42 - 28 - 21 - 14 - 12 - 7 - 6 - 4 - 3 - 2 = g(84) = -55. MATHEMATICA Select[ Range[5500], DivisorSigma[1, # ] == 2# + 56 &] (* Robert G. Wilson v, Dec 22 2004 *) PROG (Magma) [n: n in [1..10^4] |DivisorSigma(1, n) eq 2*n+56]; // Vincenzo Librandi, Jul 30 2015 CROSSREFS Cf. A005101, A033880. Cf. A141545, A141546. Sequence in context: A099637 A274348 A143758 * A141502 A039499 A341128 Adjacent sequences: A101257 A101258 A101259 * A101261 A101262 A101263 KEYWORD nonn,easy AUTHOR Vassil K. Tintschev (tinchev(AT)sunhe.jinr.ru), Dec 17 2004 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 29 12:41 EST 2023. Contains 367445 sequences. (Running on oeis4.)