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%I #18 Sep 08 2022 08:46:13
%S 6,150,180150,519264540150,8628341205030630049260150,
%T 4764689404827483203666304150636608674826622242700150
%N (7^(2^n) - 1) / 2^(n+2).
%C (m^(2^n)-1)/2^(n+2) is an integer for any odd value of m and n>0.
%C The next term, a(7), has 106 decimal digits.
%F a(n) == 150 (mod 10^4) for all n > 1. - _M. F. Hasler_, Aug 11 2015
%e a(3) = (7^8 - 1)/2^5 = 180150.
%t Table[(7^(2^n) - 1)/2^(n + 2), {n, 1, 7}] (* _Vincenzo Librandi_, Aug 09 2015 *)
%o (PARI) first(m)=vector(m,i, (7^(2^i)-1)/2^(i+2)); /* _Anders Hellström_, Aug 08 2015 */
%o (Magma) [(7^(2^n)-1)/2^(n+2): n in [1..10]]; // _Vincenzo Librandi_, Aug 09 2015
%o (PARI) A261066(n)=7^2^n>>(n+2) \\ _M. F. Hasler_, Aug 11 2015
%Y Cf. A059723, A068531, A097421.
%K nonn
%O 1,1
%A _Marco Ripà_, Aug 08 2015
%E a(5) corrected by _Vincenzo Librandi_, Aug 09 2015
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