The On-Line Encyclopedia of Integer Sequences (OEIS)

A105091 revision #1

A105091

Sum of the right diagonal in ordered 3 X 3 prime squares.

33, 133, 253, 383, 537, 691, 829, 1003, 1169, 1333, 1495, 1703, 1855, 2015, 2217, 2417, 2589, 2781, 2977, 3143, 3313, 3537, 3725, 3899, 4157, 4349, 4511, 4713, 4871, 5113, 5317, 5563, 5747, 5987, 6183, 6377, 6607, 6827, 7025, 7187, 7391, 7673, 7927

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

FORMULA

An ordered 3 X 3 prime square is 9 consecutive primes arranged in a square of the form p(9n-8) p(9n-7) p(9n-6) p(9n-5) p(9n-4) p(9n-3) p(9n-2) p(9n-1) p(9n) n=1,2,.. Right diagonal is p(9n-6 p(9n-4) p(9n-2)

EXAMPLE

The first 3 X 3 prime square

2 3 5

7 11 13

17 19 23

sum of right diagonal = 5 + 11 + 17 = 33 the first entry.

PROG

(PARI) sum3x3right(n) = { local(x, j, s); forstep(x=0, n, 9, s=0; forstep(j=3, 7, 2, s += prime(x+j); ); print1(s", ") ) }

CROSSREFS

Sequence in context: A043502 A044365 A044746 * A158588 A232538 A231758

Adjacent sequences: A105088 A105089 A105090 * A105092 A105093 A105094

KEYWORD

easy,nonn,new

AUTHOR

Cino Hilliard (hillcino368(AT)hotmail.com), Apr 07 2005

STATUS

approved