1,1

sp(5)=14=2*7 and 7-2=5, sp(80)=249=3*83 and 83-3=80, sp(86)=267=3*89 and 89-3=86; sp(n)=nth semiprime.

(PARI/gp from M. F. Hasler)

{ n=0; j=1; /* n=3068365-1; j=613668; */

while( l=(j\10^4+1)*10^4, until( l < j++, until(bigomega(n+=1)==2, );

if(2!=#f=factor(n)[, 1], next); if(j==f[2]-f[1], print("\n", [j, n, f])));

print1(j-1, ":"n", "))}

Cf. A084126, A084127, A109313, A064910.

Adjacent sequences: A131281 A131282 A131283 this_sequence A131285 A131286 A131287

Sequence in context: A141828 A134531 A062250 this_sequence A105917 A144344 A062364

more,nonn

Zak Seidov (zakseidov(AT)yahoo.com), Sep 25 2007

n=613668 (p=5, q=613673) from M. F. Hasler (maximilian.hasler(AT)gmail.com), Sep 28 2007