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A101757
Indices of semiprimes in A000073.
4
5, 12, 18, 42, 44, 50, 58, 67, 74, 83, 90, 95, 126, 142, 194, 210, 211, 275, 367, 382, 479, 655, 734, 818, 839, 926, 939, 1047
OFFSET
1,1
COMMENTS
a(29) >= 1091. A000073(1091) is a 288-digit composite number with unknown factorization. Other possible terms are 1390, 1630, 2034, 2131, 2339, ... - Tyler Busby, Feb 09 2023
LINKS
Eric Weisstein's World of Mathematics, Semiprime
FORMULA
A000073(a(n)) = A101758(n).
MATHEMATICA
Flatten[Position[LinearRecurrence[{1, 1, 1}, {1, 1, 2}, 100], _?(PrimeOmega[ #]==2&)]]+1 (* This generates the first 12 terms of the sequence. To generate more, increase 100 to a higher number, but it will take increasingly long to run. *) (* Harvey P. Dale, May 31 2013 *)
CROSSREFS
Equivalent sequence for primes: A303263.
Sequence in context: A314290 A246300 A294143 * A174518 A109403 A093084
KEYWORD
nonn,more,less
AUTHOR
EXTENSIONS
More terms from David Wasserman, Apr 03 2008
STATUS
approved