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A036449 Values square, differences triangular. 2
0, 1, 4, 25, 196, 1681, 2116, 18769, 168100, 1510441, 13586596, 14577124, 15856324, 16120225, 16289296, 16736281, 150601984, 151782400, 1365967681, 1368334081, 1393379584, 1640655025, 1649578225, 1669212736, 1725737764 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..145

MATHEMATICA

triangularQ[n_] := IntegerQ[Sqrt[8n + 1]]; a[1] = 0; a[n_] := a[n] = (b = Sqrt[a[n-1]]; While[b++; ! triangularQ[b^2 - a[n-1]]]; b^2); Table[a[n], {n, 1, 25}] (* Jean-Fran├žois Alcover, Oct 04 2011 *)

PROG

(Haskell)

a036449 n = a036449_list !! (n-1)

a036449_list = map fst listsOfValsAndDiffs

a189475 n = a189475_list !! (n-1)

a189475_list = tail $ map snd listsOfValsAndDiffs

listsOfValsAndDiffs = (0, 1) : f (0, 1) where

   f (x, y) = (u, v) : f (u, v) where

     u = x + v

     v = head $ dropWhile ((== 0) . a010052 . (+ x)) $ tail a000217_list

-- Reinhard Zumkeller, Apr 23 2011

CROSSREFS

Cf. A000217, A010052, A000290, A010054, A189475 (first differences).

Sequence in context: A171791 A060908 A322442 * A051500 A206179 A151342

Adjacent sequences:  A036446 A036447 A036448 * A036450 A036451 A036452

KEYWORD

nonn,nice

AUTHOR

David W. Wilson

EXTENSIONS

Offset corrected by Donovan Johnson, Jan 20 2011

STATUS

approved

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Last modified February 29 09:29 EST 2020. Contains 332355 sequences. (Running on oeis4.)