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A122460 Triangular array of averages of two odd primes. 0
4, 7, 6, 10, 9, 9, 13, 12, 12, 12, 17, 17, 15, 15, 15, 22, 21, 19, 20, 18, 18, 25, 24, 24, 24, 22, 23, 21, 31, 29, 27, 27, 27, 27, 25, 26, 35, 33, 33, 32, 30, 30, 30, 30, 30, 38, 38, 37, 36, 36, 35, 33, 33, 35, 34, 43, 42, 40, 41, 40, 39, 39, 38, 38, 37, 39, 50, 47, 45, 45, 43 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..71.

FORMULA

T(n,k) = (1/2)*(p(k)+p(2n+1-k)) for k=1,2,...,n, where p(1)=3, p(2)=5, ... are the odd primes.

EXAMPLE

First six rows:

4

7 6

10 9 9

13 12 12 12

17 17 15 15 15

22 21 19 20 18 18

Row 3 is formed from the first 6 odd primes:

3 5 7 11 13 17 --> (3+17)/2 (5+13)/2 (7+11)/2

CROSSREFS

Cf. A122459.

Sequence in context: A069286 A079354 A255248 * A256659 A063845 A188730

Adjacent sequences:  A122457 A122458 A122459 * A122461 A122462 A122463

KEYWORD

nonn,tabl

AUTHOR

Clark Kimberling, Sep 08 2006

STATUS

approved

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Last modified August 1 17:43 EDT 2021. Contains 346402 sequences. (Running on oeis4.)