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Search: id:A131867
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| 4, 6, 10, 22, 46, 93, 202, 407, 849, 1774, 3693, 7671, 15999, 33146, 68703, 142682, 295003, 610757, 1261573, 2603453, 5369633, 11058907, 22758881
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OFFSET
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0,1
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COMMENT
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The PARI code allows one to resume at the k-th semiprime, e.g. SP(295003,65536), and to change the output interval, e.g. SP(_,_,10) = A114125, SP(_,_,-1) = A001358.
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FORMULA
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a(n)=A001358(2^n)
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EXAMPLE
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a(0)=4 is the 1st semiprime, a(1)=6 is the 2nd semiprime ; a(16)=295003 is the 65536-th semiprime.
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PROGRAM
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(PARI) SP( n=0 /*tested number*/, c=0 /*count of semiprimes*/, step=2)={ local( l=c+!c ); /* negative/positive step means arithmetic/geometric progression of output threshold l */ until( 0, until(l<=c++, until(bigomega(n+=1)==2, )); print1(/*c ":" */ n ", "); if(step>0, l*=step, l-=step))}
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CROSSREFS
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Cf. A001358 (semiprimes), A114125.
Sequence in context: A076995 A096817 A077065 this_sequence A032392 A136838 A109378
Adjacent sequences: A131864 A131865 A131866 this_sequence A131868 A131869 A131870
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KEYWORD
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more,nonn
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AUTHOR
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M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Oct 04 2007
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