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 A053245 Numbers n such that both A053238(n) and A053238(n+1) = 1. 8
 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 (list; graph; refs; listen; history; text; internal format)
 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: A135286 A177725 A264444 * A115882 A277553 A260093 Adjacent sequences:  A053242 A053243 A053244 * A053246 A053247 A053248 KEYWORD nonn AUTHOR Asher Auel (asher.auel(AT)reed.edu) Jan 10, 2000 STATUS approved

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