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A275030 a(1) = 2. a(n) is the smallest prime such that a(n) - a(n-1) is a triangular number. 1

%I #9 Nov 27 2016 22:02:09

%S 2,3,13,19,29,107,113,149,227,233,239,317,353,359,479,557,563,569,647,

%T 653,659,1187,1193,1229,1307,1373,1409,1487,1493,1499,1619,1697,1733,

%U 1811,1847,1913,1949,2027,2063,2069,2447,2657,2663,2699,2777,2843,2879,2957,2963

%N a(1) = 2. a(n) is the smallest prime such that a(n) - a(n-1) is a triangular number.

%t triQ[n_]:=IntegerQ[Sqrt[8n+1]];

%t NestList[(x=NextPrime[#]; While[!triQ[x-#],x=NextPrime[x]];x)&,2,100]

%o (PARI) lista(nn) = {print1(p = 2, ", "); for (n=2, nn, q = nextprime(p+1); while (! ispolygonal(q-p, 3), q = nextprime(q+1)); print1(q, ", "); p = q;);} \\ _Michel Marcus_, Nov 13 2016

%Y Cf. A278139.

%K easy,nonn

%O 1,1

%A _Ivan N. Ianakiev_, Nov 13 2016

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Last modified March 28 05:02 EDT 2024. Contains 371235 sequences. (Running on oeis4.)