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A272308
Lesser of two consecutive semiprimes whose sum is prime.
5
9, 14, 21, 22, 26, 33, 35, 62, 74, 82, 86, 115, 141, 155, 158, 226, 259, 267, 295, 326, 346, 358, 362, 393, 417, 453, 482, 623, 703, 718, 734, 771, 799, 914, 933, 934, 955, 995, 1011, 1041, 1043, 1142, 1154, 1174, 1195, 1286, 1294, 1346, 1363, 1401, 1438, 1522, 1538, 1603, 1655
OFFSET
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
26 is in the sequence because 26 = 2*13, the next semiprime is 33 = 3*11, and 26+33 = 59 is prime.
MATHEMATICA
L = Select[Range@1660, PrimeOmega@# == 2 &]; Pick[Most@L, PrimeQ[Plus @@@ Partition[L, 2, 1]]] (* Giovanni Resta, Apr 25 2016 *)
PROG
(PARI) proxsem(n)=my(p=n, s, r); while(s==0, p++; if(bigomega(p)==2, s=1; r=p)); p
for(i=1, 2000, if(bigomega(i)==2, a=proxsem(i)+i; if(isprime(a), print1(i, ", "))))
(PARI) list(lim)=my(v=List(), u=v); lim\=1; while(bigomega(lim++)!=2, ); forprime(p=2, lim\2, forprime(q=2, lim\p, listput(v, p*q))); v=Set(v); for(i=1, #v-1, if(isprime(v[i+1]+v[i]), listput(u, v[i]))); Set(u) \\ Charles R Greathouse IV, Apr 29 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, Apr 25 2016
STATUS
approved