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A226429
Number of numerical semigroups S of genus 3^n having a minimal generating set of cardinality 2.
0
2, 3, 4, 4, 5, 7, 8, 9, 8, 9, 11, 13, 11, 15, 16, 14, 14, 18, 20, 21
OFFSET
1,1
LINKS
Shalom Eliahou and Jorge Ramírez Alfonsín, Two-generator numerical semigroups and Fermat and Mersenne numbers, SIAM J. Discrete Math., 25(2), 2011, 622-630.
FORMULA
a(n) = n + 1 if 2*3^n - 1 is prime.
a(n) ~ n + 1.
CROSSREFS
Sequence in context: A036416 A084618 A075518 * A036820 A017829 A017843
KEYWORD
nonn,more
AUTHOR
STATUS
approved