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A005521 1 + (sum of first n odd primes - n)/2. 2
1, 2, 4, 7, 12, 18, 26, 35, 46, 60, 75, 93, 113, 134, 157, 183, 212, 242, 275, 310, 346, 385, 426, 470, 518, 568, 619, 672, 726, 782, 845, 910, 978, 1047, 1121, 1196, 1274, 1355, 1438, 1524, 1613, 1703, 1798 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..42.

FORMULA

a(n+1) = a(n) + (prime(n+1) - 1)/2 for odd primes prime(n+1).

CROSSREFS

a(n+1) - 1 counts primorial intervals A065917. a(n+2) - 2*a(n+1) + a(n) = A028334(n). - Frank Ellermann

Sequence in context: A011910 A227590 A267529 * A135901 A124197 A011909

Adjacent sequences:  A005518 A005519 A005520 * A005522 A005523 A005524

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified August 3 07:58 EDT 2021. Contains 346435 sequences. (Running on oeis4.)