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A175459 a(1)=4. a(n) = a(n-1) + n, if a(n-1)+n is composite. Otherwise a(n) = a(n-1)*n. 1

%I

%S 4,6,9,36,180,186,1302,1310,11790,11800,11811,11823,11836,11850,11865,

%T 11881,11898,11916,11935,11955,11976,11998,12021,12045,12070,12096,

%U 12123,12151,12180,12210,378510,378542,378575,378609,378644,378680

%N a(1)=4. a(n) = a(n-1) + n, if a(n-1)+n is composite. Otherwise a(n) = a(n-1)*n.

%C Each term is composite.

%p A175459 := proc(n) option remember; if n =1 then 4; else if isprime( procname(n-1)+n) then procname(n-1)*n; else procname(n-1)+n ; end if; end if; end proc:

%p seq(A175459(n),n=1..120) ; # _R. J. Mathar_, May 28 2010

%K nonn

%O 1,1

%A _Leroy Quet_, May 20 2010

%E More terms from _R. J. Mathar_, May 28 2010

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Last modified July 21 05:26 EDT 2019. Contains 325190 sequences. (Running on oeis4.)