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 A098166 a(n) is the prime index of the Lesser Fortunate number A055211(n), or 0 if A055211(n) is not a prime. 4
 2, 4, 5, 6, 7, 10, 9, 14, 13, 21, 17, 15, 24, 19, 21, 28, 24, 26, 31, 25, 23, 24, 25, 54, 32, 30, 36, 56, 54, 48, 41, 77, 60, 36, 45, 40, 52, 51, 43, 48, 48, 62, 108, 62, 88, 49, 64, 74, 55, 63, 65, 111, 69, 66, 63, 123, 91, 66, 83, 92, 97, 110, 67, 75, 99, 87 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS Jinyuan Wang, Table of n, a(n) for n = 2..2000 FORMULA a(n) = A000720(A055211(n)) iff A055211(n) is a prime. - Michel Marcus, Oct 05 2019 PROG (PARI) a(n) = {my(k = prod(j=1, n, prime(j))); p = k-precprime(k-2); if(isprime(p), primepi(p), 0); } \\ Jinyuan Wang, Oct 02 2019 CROSSREFS Cf. A000720, A055211, A098167. Sequence in context: A138620 A260820 A248554 * A217445 A007238 A083875 Adjacent sequences:  A098163 A098164 A098165 * A098167 A098168 A098169 KEYWORD nonn AUTHOR Pierre CAMI, Aug 30 2004 EXTENSIONS Name edited by and more terms from Jinyuan Wang, Oct 02 2019 STATUS approved

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Last modified August 4 11:01 EDT 2021. Contains 346447 sequences. (Running on oeis4.)