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A002120 a(1) = 0, a(2) = -2; for n > 2, a(n) + a(n-2) - a(n-3) - a(n-5) - ... - a(n-p) = (-1)^(n+1)*n if n is prime, otherwise = 0, where p = largest prime < n.
(Formerly M0414 N0158)
5

%I M0414 N0158 #17 Oct 14 2023 22:34:34

%S 0,-2,3,2,0,1,7,2,-6,8,22,-7,0,33,3,-14,51,46,-19,12,94,42,-23,113,

%T 150,-54,48,345,116,-109,403,498,-140,219,1057,326,-259,1271,1641,

%U -308,656,3396,1161,-790,4269,5357,-987,2257,10934,3958,-1986,13678,17278,-2492,7447,35569,13778,-5860,44368,56403,-6405

%N a(1) = 0, a(2) = -2; for n > 2, a(n) + a(n-2) - a(n-3) - a(n-5) - ... - a(n-p) = (-1)^(n+1)*n if n is prime, otherwise = 0, where p = largest prime < n.

%C Arises in studying the Goldbach conjecture.

%D P. A. MacMahon, Properties of prime numbers deduced from the calculus of symmetric functions, Proc. London Math. Soc., 23 (1923), 290-316. [Coll. Papers, Vol. II, pp. 354-382] [The sequence e_n]

%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H N. J. A. Sloane, <a href="/A002120/b002120.txt">Table of n, a(n) for n = 1..1000</a>

%H P. A. MacMahon, <a href="http://plms.oxfordjournals.org/content/s2-23/1/290.extract">Properties of prime numbers deduced from the calculus of symmetric functions</a>, Proc. London Math. Soc., 23 (1923), 290-316. = Coll. Papers, II, pp. 354-380.

%F a(n) = (-1)^(n+1)*n*A010051(n)+Sum_{k=1..n-1} (-1)^(n-k+1)*A010051(n-k)*a(k). - _Vladeta Jovovic_, May 08 2003

%p M:=90; e:=array(0..M); e[1]:=0; e[2]:=-2; for n from 3 to M do t1:=-e[n-2]; if isprime(n) then t1:=t1+(-1)^(n+1)*n; fi; for k from 2 to n do p := ithprime(k); if p < n then t1 := t1 + e[n-p]; fi; od: e[n]:=t1; od: [seq(e[n],n=1..M)];

%K sign

%O 1,2

%A _N. J. A. Sloane_

%E More terms from _Vladeta Jovovic_, May 08 2003

%E Edited by _N. J. A. Sloane_, Dec 03 2006

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