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 A119556 Primes in the sequence f(n+1) = f(n)+((-1)^(n+1))*n!, with f(1)=0. 1
 5, 101, 4421, 1226280710981, 115578717622022981, 32656499591185747972776747396512425885838364422981, 136372385605079432248118270297843987319730859689490659519593045108637838364422981 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The tenth term has 1579 digits. - Harvey P. Dale, Sep 10 2018 REFERENCES G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008, p. 160. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..9 EXAMPLE f(0)=0, f(1) = 0+((-1)^2)*1! = 1, f(2) = 1+((-1)^3)*2! = -1, f(3) = -1+((-1)^4)*3! = 5, which is prime, so 5 is the first term of the sequence. MAPLE P:=proc(n) local i, j; j:=0; for i from 1 by 1 to n do j:=j+((-1)^(i+1))*i!; if isprime(j) then print(i); fi; od; end: P(100); MATHEMATICA nxt[{n_, a_}]:={n+1, a+(-1)^(n+1) n!}; Select[NestList[nxt, {1, 0}, 205][[All, 2]], #>0 && PrimeQ[#]&] (* Harvey P. Dale, Sep 10 2018 *) CROSSREFS Sequence in context: A266452 A074790 A009757 * A009765 A113073 A275749 Adjacent sequences:  A119553 A119554 A119555 * A119557 A119558 A119559 KEYWORD nonn,easy AUTHOR Paolo P. Lava and Giorgio Balzarotti, May 30 2006 EXTENSIONS Offset changed to 1 (this is a list) from Bruno Berselli, Feb 16 2012 Definition corrected by Harvey P. Dale, Sep 10 2018 STATUS approved

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Last modified August 3 13:49 EDT 2020. Contains 336198 sequences. (Running on oeis4.)