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A131284
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Numbers n such that difference between prime factors of n-th semiprime is n.
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13
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OFFSET
| 1,1
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COMMENTS
| The 6384425704th semiprime is 44690979977 = 7*6384425711. 6384425711-7 = 6384425704. [From Donovan Johnson (donovan.johnson(AT)yahoo.com), Jul 11 2010]
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EXAMPLE
| 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.
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PROG
| (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", "))}
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CROSSREFS
| Cf. A084126, A084127, A109313, A064910.
Sequence in context: A141828 A134531 A062250 * A105917 A144344 A062364
Adjacent sequences: A131281 A131282 A131283 * A131285 A131286 A131287
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KEYWORD
| more,nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Sep 25 2007
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EXTENSIONS
| n=613668 (p=5, q=613673) from M. F. Hasler (maximilian.hasler(AT)gmail.com), Sep 28 2007
a(5) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jul 11 2010
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