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A158339 Semiprimes that are the sum of four successive semiprimes. 4
39, 94, 106, 118, 146, 158, 185, 201, 221, 254, 302, 365, 427, 473, 485, 519, 537, 589, 633, 655, 707, 723, 749, 767, 842, 851, 869, 901, 1003, 1145, 1205, 1211, 1219, 1247, 1263, 1337, 1349, 1603, 1646, 1681, 1703, 1731, 1797, 1891, 1903, 1937, 2005, 2019 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Zak Seidov, Table of n, a(n) for n = 1..100000

EXAMPLE

a(1)=39=6+9+10+14, or A001358(15)=A001358(2)+A001358(3)+A001358(4)+A001358(5).

MATHEMATICA

Select[Total/@Partition[Select[Range[600], PrimeOmega[#]==2&], 4, 1], PrimeOmega[ #]==2&] (* Harvey P. Dale, Aug 14 2014 *)

PROG

(PARI) issemi(n)=bigomega(n)==2

list(lim)=if(lim<39, return([])); my(v=List(), u=v, x=lim\4+log(lim)*4\1+9); forprime(p=2, x\2, forprime(q=2, min(x\p, p), listput(u, p*q))); u=Set(u); while(u[#u-2]+u[#u-1]+u[#u]+x+1<=lim, while(!issemi(x++), ); u=concat(u, x)); for(i=1, #u-3, u[i]+=u[i+1]+u[i+2]+u[i+3]); u[#u-2]=u[#u-1]=u[#u]=1; forprime(p=2, lim\2, forprime(q=2, min(lim\p, p), listput(v, p*q))); setintersect(Set(v), u) \\ Charles R Greathouse IV, Mar 05 2017

CROSSREFS

Semiprimes that are the sum of k successive semiprimes: A131610 (k=3), A092192 (k=2), A001358 (k=1).

Sequence in context: A043245 A044025 A062668 * A211499 A126077 A276401

Adjacent sequences:  A158336 A158337 A158338 * A158340 A158341 A158342

KEYWORD

nonn

AUTHOR

Zak Seidov, Mar 16 2009

STATUS

approved

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Last modified May 23 18:42 EDT 2017. Contains 286926 sequences.