A242209 Semiprimes sp = p^2 + q^2 + r^2 where p, q and r are consecutive primes.
38, 339, 579, 1731, 5739, 8499, 32259, 133851, 145779, 163851, 207579, 222531, 235779, 260187, 308019, 323619, 366819, 469731, 550491, 644979, 684699, 743091, 926427, 1003539, 1242939, 1743531, 1808259, 1852107, 1909059, 2075091, 2585571, 4226979, 5358291
Offset: 1
Keywords
Examples
a(1) = 38 = 2^2 + 3^2 + 5^2 = 2*19 is semiprime. a(2) = 339 = 7^2 + 11^2 + 13^2 = 3*113 is semiprime.
Links
- K. D. Bajpai, Table of n, a(n) for n = 1..5100
Programs
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Maple
with(numtheory): A242209:= proc()local k ; k:=(ithprime(x)^2+ithprime(x+1)^2+ithprime(x+2)^2); if bigomega(k)=2 then RETURN (k); fi;end: seq(A242209 (),x=1..500);
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Mathematica
Select[Total[#^2]&/@Partition[Prime[Range[300]],3,1],PrimeOmega[#]==2&] (* Harvey P. Dale, Nov 05 2015 *)
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PARI
for(k=1, 500, sp=prime(k)^2+prime(k+1)^2+prime(k+2)^2; if(bigomega(sp)==2, print1(sp, ", "))) \\ Colin Barker, May 07 2014
Comments