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%I #11 Jul 15 2021 21:23:03
%S 1,20,49,65,103,176,279,284,299,437,513,553,656,973,1271,1779,1921,
%T 2156,2312,2347,2554,2759,3176,3379,4008,4028,4132,5255,6354,6764,
%U 7116,8299,8334,8366,8723,9277,9755,10092,10475,10631,11429,11842,12633,13157,13627
%N Numbers k such that k + prime(k) gives a triangular number.
%H T. D. Noe, <a href="/A115882/b115882.txt">Table of n, a(n) for n = 1..1000</a>
%e 103 + prime(103) = 103 + 563 = 666 = T(36).
%t TriangularQ[n_] := IntegerQ[Sqrt[1 + 8*n]]; Select[Range[20000], TriangularQ[# + Prime[#]] &] (* _T. D. Noe_, Jan 27 2014 *)
%o (PARI) isok(n) = ispolygonal(n + prime(n), 3); \\ _Michel Marcus_, Jan 25 2014
%Y Cf. A064371, A115883, A115886.
%K nonn
%O 1,2
%A _Giovanni Resta_, Feb 06 2006
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