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 A249622 a(n) = number of ways to express A117048(n) as the sum of two positive triangular numbers. 2

%I

%S 1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,3,2,1,1,3,1,2,1,1,2,1,3,1,

%T 2,1,2,1,1,2,1,1,2,2,1,1,2,2,1,1,4,1,3,1,1,1,1,1,1,2,2,2,2,2,1,1,1,1,

%U 1,1,1,2,4,1,1,1,3,1,1,2,1,2,2,1,1,2,1,1,3,1,2,1,2,1,1,6,2,1,1,1,1

%N a(n) = number of ways to express A117048(n) as the sum of two positive triangular numbers.

%H Zak Seidov, <a href="/A249622/b249622.txt">Table of n, a(n) for n = 1..10000</a>

%e a(6) = 2 because A117048(6) = 31 and 31 = 3 + 28 = 10 + 21 (first case of two-way expression).

%e a(22) = 3 because A117048(22) = 181 and 181 = A000217(i) + A000217(k), for {i,k} = {{4, 18}, {7, 17}, {9, 16}} (first case of three-way expression): 181 = 10 + 171 = 28 + 153 = 45 + 136.

%Y Cf. A000040, A000217, A002383.

%K nonn

%O 1,6

%A _Zak Seidov_, Nov 03 2014

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Last modified June 19 23:01 EDT 2019. Contains 324222 sequences. (Running on oeis4.)