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a(n) = prime(n)^2 - 2.
10

%I #35 Aug 02 2023 18:17:30

%S 2,7,23,47,119,167,287,359,527,839,959,1367,1679,1847,2207,2807,3479,

%T 3719,4487,5039,5327,6239,6887,7919,9407,10199,10607,11447,11879,

%U 12767,16127,17159,18767,19319,22199,22799,24647,26567,27887

%N a(n) = prime(n)^2 - 2.

%C Smallest numbers k such that k*prime(n)^2 + 1 is a square. - _Bruno Berselli_, Apr 19 2013

%H Vincenzo Librandi, <a href="/A049001/b049001.txt">Table of n, a(n) for n = 1..1000</a>

%H Barry Brent, <a href="https://arxiv.org/abs/2212.12515">On the constant terms of certain meromorphic modular forms for Hecke groups</a>, arXiv:2212.12515 [math.NT], 2022.

%H Barry Brent, <a href="https://doi.org/10.20944/preprints202306.1164.v6">On the Constant Terms of Certain Laurent Series</a>, Preprints (2023) 2023061164.

%F a(n) = A001248(n) - 2.

%F a(n) = A182200(n) + 1. - _Wesley Ivan Hurt_, Oct 11 2013

%F Product_{n>=1} (1 - 1/a(n)) = A065481. - _Amiram Eldar_, Nov 07 2022

%p A049001:=n->ithprime(n)^2-2; seq(A049001(k), k=1..50); # _Wesley Ivan Hurt_, Oct 11 2013

%t Table[Prime[n]^2-2, {n, 50}] (* _Wesley Ivan Hurt_, Oct 11 2013 *)

%o (Haskell)

%o a049001 = subtract 2 . a001248 -- _Reinhard Zumkeller_, Jul 30 2015

%o (PARI) a(n) = prime(n)^2 - 2; \\ _Amiram Eldar_, Nov 07 2022

%Y Cf. A001248, A049002, A065481.

%Y Cf. A084920, A166010, A182200; A182174.

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_