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 A098961 Sums of two squares and divisible by 13. 2
 13, 26, 52, 65, 104, 117, 130, 169, 208, 221, 234, 260, 325, 338, 377, 416, 442, 468, 481, 520, 533, 585, 637, 650, 676, 689, 754, 793, 832, 845, 884, 936, 949, 962, 1040, 1053, 1066, 1105, 1157, 1170, 1261, 1274, 1300, 1313 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA a(n) = 13 * A001481(n+1) for n >= 1. - Joerg Arndt, Dec 03 2022 EXAMPLE Sums not divisible by 13 are shown in asterisks: . | 1 4 9 16 25 36 49 64 81 100 121 ----+------------------------------------------------------ 1 | * * * * 26 * * 65 * * * 4 | * * 13 * * * * * * 104 * 9 | * 13 * * * * * * * * 130 16 | * * * * * 52 65 * * * * 25 | 26 * * * * * * * * * * 36 | * * * 52 * * * * 117 * * 49 | * * * 65 * * * * 130 * * 64 | 65 * * * * * * * * * * 81 | * * * * * 117 130 * * * * 100 | * 104 * * * * * * * * 221 121 | * * 130 * * * * * * 221 * MAPLE filter:= proc(n) local t, F; F:= select(t -> t[2]::odd, ifactors(n)[2]); andmap(t -> t[1] = 2 or t[1] mod 4 = 1, F); end proc: select(filter, [seq(i, i=13..10000, 13)]); # Robert Israel, Dec 02 2022 MATHEMATICA With[{nn=50}, Take[Union[Select[Total/@Subsets[Range[nn]^2, {2}], Divisible[ #, 13]&]], nn]] (* Harvey P. Dale, Aug 15 2014 *) CROSSREFS Intersection of A001481 and A008595. Cf. A094447. Sequence in context: A044838 A033010 A019551 * A033897 A005029 A251149 Adjacent sequences: A098958 A098959 A098960 * A098962 A098963 A098964 KEYWORD nonn AUTHOR Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Oct 22 2004 STATUS approved

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Last modified April 18 22:18 EDT 2024. Contains 371782 sequences. (Running on oeis4.)