A108190 4-almost primes equal to the sum of two successive semiprimes.

24, 36, 100, 184, 189, 372, 472, 484, 513, 532, 580, 644, 748, 824, 904, 940, 1016, 1029, 1036, 1062, 1068, 1096, 1107, 1164, 1180, 1208, 1225, 1236, 1269, 1284, 1304, 1336, 1340, 1395, 1420, 1430, 1444, 1482, 1508, 1521, 1580, 1593, 1610, 1628, 1666

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

a(1) = 24 because 2*5 + 2*7 = 10 + 14 = 24 = 2*2*2*3.
a(5) = 189 because 2*47 + 5*19 = 94 + 95 = 189 = 3*3*3*7.
a(11) = 513 because 2*127 + 7*37 = 254 + 259 = 513 = 3*3*3*19.

Mathematica

Select[Total/@Partition[Select[Range[2000], PrimeOmega[#]==2&], 2, 1], PrimeOmega[ #] ==4&] (* Harvey P. Dale, Apr 26 2018 *)

Prog

(PARI) list(lim)=my(u=List(), L=lim\2); forprime(p=2, L\2, forprime(q=2, min(p, L\p), listput(u, p*q))); for(k=L+1, 2*L, if(bigomega(k)==2, listput(u, k); break)); u=Set(u); for(i=2, #u, u[i-1]=u[i]+u[i-1]); if(u[#u]>lim, u[#u]=0); select(k->bigomega(k)==4, u) \\ Charles R Greathouse IV, Feb 05 2017

Crossrefs

Sequence in context: A278474 A327946 A288949 * A185489 A303884 A304616

Adjacent sequences: A108187 A108188 A108189 * A108191 A108192 A108193

Keyword

easy,nonn

Author

Giovanni Teofilatto, Jun 15 2005

Extensions

Corrected and extended by Ray Chandler, Jul 07 2005

Status

approved