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A227249 Number of consecutive composites beginning with the first, to be added to obtain a power. 2
1, 4, 6, 21, 80, 4151, 6982, 269563, 779693, 834365, 16176645, 19770092, 41049539, 228612936, 1950787140, 2404785364, 3095996836, 5236785750 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

All powers are squares with the exception of 3^3 for a(2) and 6^9 for a(6). I conjecture these are the only nonsquare powers.

a(19) > 10^10. - Zak Seidov, Jul 06 2013

LINKS

Table of n, a(n) for n=1..18.

FORMULA

{n: A053767(n) in A001597}. -  Zak Seidov, Jul 06 2013

EXAMPLE

Considering 1 not to be prime and not to be composite, first composite is 4 which is 2^2. And the sum of the four first composites is: 4 + 6 + 8 + 9 = 27 = 3^3.

MAPLE

# see A001597 for isA001597

for n from 1 do

    if isA001597(A053767(n) ) then

        print(n) ;

    end if;

end do: # R. J. Mathar, Jul 08 2013

PROG

(PARI) : n=10^7; v=vector(n); i=0; for(a=2, n, if(isprime(a), next, i++; v[i]=a)); k=0; for(j=1, i, k=k+v[j]; if(ispower(k, , &n), print1([k, n, j], " ")))

CROSSREFS

Cf. A001597, A002808, A053767, A141092.

Sequence in context: A229743 A151520 A282517 * A002270 A286358 A088228

Adjacent sequences:  A227246 A227247 A227248 * A227250 A227251 A227252

KEYWORD

nonn,more

AUTHOR

Robin Garcia, Jul 04 2013

EXTENSIONS

a(11) - a(18) from Zak Seidov, Jul 06 2013

STATUS

approved

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Last modified May 29 21:28 EDT 2017. Contains 287257 sequences.