A053245 Numbers n such that both A053238(n) and A053238(n+1) = 1.

20, 49, 56, 79, 108, 132, 145, 170, 177, 230, 253, 277, 289, 307, 347, 382, 405, 412, 424, 437, 495, 548, 585, 592, 633, 645, 704, 734, 752, 764, 789, 802, 841, 854, 930, 943, 967, 974, 1005, 1012, 1053, 1066, 1130, 1154, 1179, 1186, 1216, 1223, 1264

Offset

1,1

Comments

Pairs of consecutive 1's occur uncommonly often in A053238.

Links

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

Maple

with(numtheory): f := [seq( `if`((sigma(i) > sigma(i+1)), i, print( )), i=1..5000)];
seq(`if`((f[i+2]-f[i+1]=1) and (f[i+1]-f[i]=1), i, print( )), i=1..1500);

Prog

(Haskell)
a053245 n = a053245_list !! (n-1)
a053245_list = f a053242_list where
   f (x:x':xs) | x' == x+1 = x : f xs
               | otherwise = f (x':xs)
-- Reinhard Zumkeller, Oct 16 2011

Crossrefs

Cf. A000203, A053226, A053238, A053239, A053240, A053241, A053242, A053243, A053244.

Sequence in context: A338235 A177725 A264444 * A115882 A303295 A277553

Adjacent sequences: A053242 A053243 A053244 * A053246 A053247 A053248

Keyword

nonn

Author

Asher Auel, Jan 10 2000

Status

approved