A081028 - OEIS

A081028

Numbers n such that n-th term of A080997 is prime; a(n) is ranking of n-th prime number among the positive integers in terms of centrality (cf. A080997 for explanation of this concept).

2, 3, 6, 10, 18, 20, 25, 33, 40, 53, 56, 69, 79, 89, 95, 108

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OFFSET

1,1

COMMENTS

Let p(n) be the n-th prime. In order for the centrality rankings of all numbers from 1 to p(n) to be known, it is necessary for the numbers that occupy all of the ranking positions from 1 to a(n) to be determined.

LINKS

Table of n, a(n) for n=1..16.

FORMULA

Formula for centrality of n: A018804(n)/n^2 (see also A080997).

CROSSREFS

Cf. A080997, A080998.

Sequence in context: A026397 A193200 A026779 * A325232 A208479 A065441

Adjacent sequences: A081025 A081026 A081027 * A081029 A081030 A081031

KEYWORD

nonn

AUTHOR

Matthew Vandermast, Mar 02 2003

STATUS

approved