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A135145 Values of m where A020482(m) != A060308(m-1). 2

%I #20 Jul 13 2014 10:03:01

%S 49,61,64,74,95,104,110,125,146,151,154,163,166,173,184,199,205,209,

%T 215,229,238,244,250,259,266,269,278,293,314,320,335,346,350,355,359,

%U 364,376,385,391,394,398,403,410,419,424,427,436,439,448,451,454,460

%N Values of m where A020482(m) != A060308(m-1).

%C Usually the greatest p with p,q both prime, p+q = 2m, is equal to the largest prime <= 2m-2, but not always. These are the exceptions.

%C Almost all natural numbers are in the sequence so the above comment is misleading in general, and only fitting for small numbers. - _Jens Kruse Andersen_, Jul 13 2014

%H Jens Kruse Andersen, <a href="/A135145/b135145.txt">Table of n, a(n) for n = 1..10000</a>

%t a2[n_] := {p, q} /. {ToRules @ Reduce[p+q == 2*n, {p, q}, Primes]} // Max; a8[n_] := Max[FactorInteger[(2*n)!/n!^2]]; Select[Range[500], a2[#] != a8[#-1]&] (* _Jean-François Alcover_, Dec 19 2013 *)

%o (PARI) for(m=2, 1000, p=precprime(2*m-2); if(!isprime(2*m-p), print1(m", "))) \\ _Jens Kruse Andersen_, Jul 12 2014

%Y Cf. A020482, A060308.

%K nonn

%O 1,1

%A _Harry J. Smith_, Nov 20 2007

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Last modified April 25 16:45 EDT 2024. Contains 371989 sequences. (Running on oeis4.)