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 A100634 a(n) is the decimal equivalent of the binary number whose k-th least significant bit is 1 iff k is a prime number and k <= n. 2
 0, 2, 6, 6, 22, 22, 86, 86, 86, 86, 1110, 1110, 5206, 5206, 5206, 5206, 70742, 70742, 332886, 332886, 332886, 332886, 4527190, 4527190, 4527190, 4527190, 4527190, 4527190, 272962646, 272962646, 1346704470, 1346704470, 1346704470 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 1 is not considered prime. If 1 were to be considered prime, each term would be incremented by 1. LINKS T. D. Noe, Table of n, a(n) for n = 1..300 Eric Weisstein's World of Mathematics, Least Significant Bit EXAMPLE a(5)=22 because the k-th least significant bits 1,2,3,4,5 are prime for 2,3,5 and not prime for 1,4. So k=1->0, k=2->1, k=3->1, k=4->0 and k=5->1 gives the bit sequence 10110, which is 2 + 4 + 16 = 22 in its decimal expansion. MATHEMATICA Table[FromDigits[Reverse[Table[If[PrimeQ[k] == True, 1, 0], {k, 1, N}]], 2], {N, 1, 40}] PROG (PARI) Sum(an)={ L=#binary(an)-1; k=2; s=0; pow2=2; forstep(j=L, 2, -1, if(isprime(k), s+=pow2); k++; pow2*=2); return(s) }; n=1; an=0; while(an<=1346704470, an+=Sum(an); print1(an, ", "); n++; while(!isprime(n), print1(an, ", "); n++); an=2^(n-1) ) \\ Washington Bomfim, Jan 17 2011 CROSSREFS Cf. A000040, A080355, A080339, A072762. Sequence in context: A258702 A320916 A119551 * A242527 A304680 A325803 Adjacent sequences: A100631 A100632 A100633 * A100635 A100636 A100637 KEYWORD nonn,base AUTHOR Joseph Biberstine (jrbibers(AT)indiana.edu), Dec 02 2004 STATUS approved

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Last modified December 3 09:50 EST 2022. Contains 358517 sequences. (Running on oeis4.)