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A129904 Find the first two terms in A003215, say A003215(i) and A003215(j), that are divisible by a number in A016921 not 1, say by k = A016921(m). Then i + j + 1 = k and k is added to the sequence. 0
7, 13, 19, 31, 37, 43, 49, 61, 67, 73, 79, 91, 97, 103, 109, 127, 133, 139, 151, 157, 163, 169, 181, 193, 199, 211, 217, 223, 229, 241, 247, 259, 271, 277, 283, 301, 307, 313, 331, 337, 343, 349, 361, 367, 373, 379, 397, 403, 409, 421, 427, 433, 439, 457, 463 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

EXAMPLE

A003215(1) = 7 is divisible by A016921(1) = 7, A003215(5) = 91 is divisible by A016921(1) = 7 and 5+1+1=7, so 7 is a member.

MAPLE

isA129904 := proc(k)

    local i, j ;

    if modp(k, 6) = 1 and k> 1 then

        for i from 0 to k-1 do

            j := k-1-i ;

            if modp(A003215(i), k) =0 and modp(A003215(j), k) =0 then

                return true;

            end if;

        end do:

        false ;

    else

        false;

    end if;

end proc:

for k from 1 to 400 do

    if isA129904(k) then

        printf("%d, ", k) ;

    end if;

end do:

CROSSREFS

Cf. A003215, A016921.

Sequence in context: A167462 A088513 A004611 * A133290 A038590 A218146

Adjacent sequences:  A129901 A129902 A129903 * A129905 A129906 A129907

KEYWORD

nonn

AUTHOR

Mats Granvik, Jun 04 2007

EXTENSIONS

Extended by R. J. Mathar, Dec 16 2016

STATUS

approved

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Last modified January 28 09:17 EST 2020. Contains 331318 sequences. (Running on oeis4.)