A053242 Numbers n such that A053238(n) = 1.

20, 21, 49, 50, 56, 57, 79, 80, 108, 109, 132, 133, 145, 146, 155, 170, 171, 177, 178, 201, 230, 231, 253, 254, 260, 277, 278, 289, 290, 307, 308, 341, 347, 348, 376, 382, 383, 405, 406, 412, 413, 424, 425, 437, 438, 467, 495, 496, 548, 549, 555, 570, 585

Offset: 1

Author

Asher Auel, Jan 10 2000

Keywords

• nonn

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A053226, A053238, A053239, A053240, A053241, A053243, A053244, A053245 (subsequence).

Programs

Haskell

import Data.List (elemIndices)
a053242 n = a053242_list !! (n-1)
a053242_list = map (+ 1) $ elemIndices 1 a053238_list
-- Reinhard Zumkeller, Oct 16 2011

Maple

with(numtheory): f := [seq( `if`((sigma(i) > sigma(i+1)),i,print( )), i=1..5000)];
seq( `if`(f[i+1] - f[i] = 2,i,print( )), i=1..1000);