A122460 Triangular array of averages of two odd primes.

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

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: A079354 A354763 A255248 * A256659 A063845 A188730

Adjacent sequences: A122457 A122458 A122459 * A122461 A122462 A122463

Keyword

nonn,tabl

Author

Clark Kimberling, Sep 08 2006

Status

approved