The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A076530 Numbers n such that sigma(n) = sigma(n+1) - sigma(n-1). 7
 2, 3, 23, 1967, 3263, 5015, 60455, 1016507, 4420163, 12055511, 14365607, 25726727, 27896423, 66562307, 72764735, 98734967, 175186655, 224868311, 253694927, 288657203, 386668343, 421575407, 504737747, 630645455, 1493547999 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Donovan Johnson and Giovanni Resta, Table of n, a(n) for n = 1..112 (terms < 10^13, first 50 terms from Donovan Johnson) FORMULA a(n) = A065900(n) - 1 = A104149(n) + 1. - Alex Ratushnyak, Jul 06 2013 EXAMPLE sigma(24) = 60. sigma(23) = 24. sigma(22) = 36 and 24 = 60 - 36; hence 23 is a term of the sequence. MATHEMATICA Select[Range[2, 10^5], DivisorSigma[1, # ] == DivisorSigma[1, # + 1] - DivisorSigma[1, # - 1] &] Flatten[Position[Partition[DivisorSigma[1, Range[1493548000]], 3, 1], _?(#[[2]] == #[[3]]-#[[1]]&), 1, Heads->False]]+1 (* Harvey P. Dale, Apr 13 2020 *) CROSSREFS Cf. A000203, A065900, A104149. Sequence in context: A160341 A092388 A225726 * A238265 A203015 A260420 Adjacent sequences:  A076527 A076528 A076529 * A076531 A076532 A076533 KEYWORD nonn AUTHOR Joseph L. Pe, Oct 18 2002 EXTENSIONS a(8)-a(25) from Donovan Johnson, Feb 01 2009 STATUS approved

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

Last modified August 1 22:36 EDT 2021. Contains 346408 sequences. (Running on oeis4.)