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A281872 Number of sets of exactly n positive integers <= 2n having a square element sum. 3
1, 1, 1, 3, 8, 24, 74, 238, 786, 2646, 9071, 31536, 110967, 394420, 1414053, 5107523, 18568628, 67894564, 249513890, 921134164, 3414439996, 12703212213, 47419589969, 177551521838, 666655929561, 2509526456940, 9469082269965, 35807434636137, 135681047696427 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..130

FORMULA

a(n) = A281871(2n,n).

EXAMPLE

a(0) = 1: {}.

a(1) = 1: {1}.

a(2) = 1: {1,3}.

a(3) = 3: {1,2,6}, {1,3,5}, {2,3,4}.

a(4) = 8: {1,2,5,8}, {1,2,6,7}, {1,3,4,8}, {1,3,5,7}, {1,4,5,6}, {2,3,4,7}, {2,3,5,6}, {4,6,7,8}.

CROSSREFS

Cf. A281871, A284251.

Sequence in context: A291886 A275856 A303607 * A046342 A238977 A182453

Adjacent sequences:  A281869 A281870 A281871 * A281873 A281874 A281875

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jan 31 2017

STATUS

approved

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Last modified March 19 13:08 EDT 2019. Contains 321330 sequences. (Running on oeis4.)