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A261066 (7^(2^n) - 1) / 2^(n+2). 1
6, 150, 180150, 519264540150, 8628341205030630049260150, 4764689404827483203666304150636608674826622242700150 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

(m^(2^n)-1)/2^(n+2) is an integer for any odd value of m and n>0.

The next term, a(7), has 106 decimal digits.

LINKS

Table of n, a(n) for n=1..6.

FORMULA

a(n) == 150 (mod 10^4) for all n > 1. - M. F. Hasler, Aug 11 2015

EXAMPLE

a(3) = (7^8 - 1)/2^5 = 180150.

MATHEMATICA

Table[(7^(2^n) - 1)/2^(n + 2), {n, 1, 7}] (* Vincenzo Librandi, Aug 09 2015 *)

PROG

(PARI) first(m)=vector(m, i, (7^(2^i)-1)/2^(i+2)); /* Anders Hellström, Aug 08 2015 */

(MAGMA) [(7^(2^n)-1)/2^(n+2): n in [1..10]]; // Vincenzo Librandi, Aug 09 2015

(PARI) A261066(n)=7^2^n>>(n+2) \\ M. F. Hasler, Aug 11 2015

CROSSREFS

Cf. A059723, A068531, A097421.

Sequence in context: A126679 A232689 A165436 * A297737 A168654 A147796

Adjacent sequences:  A261063 A261064 A261065 * A261067 A261068 A261069

KEYWORD

nonn

AUTHOR

Marco Ripà, Aug 08 2015

EXTENSIONS

a(5) corrected by Vincenzo Librandi, Aug 09 2015

STATUS

approved

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Last modified March 30 18:46 EDT 2020. Contains 333127 sequences. (Running on oeis4.)