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 A100897 a(n) is the decimal expansion of 7nn7. 5

%I

%S 7007,7117,7227,7337,7447,7557,7667,7777,7887,7997,710107,711117,

%T 712127,713137,714147,715157,716167,717177,718187,719197,720207,

%U 721217,722227,723237,724247,725257,726267,727277,728287,729297,730307

%N a(n) is the decimal expansion of 7nn7.

%H Daniel Starodubtsev, <a href="/A100897/b100897.txt">Table of n, a(n) for n = 0..10000</a>

%F a(n) = 7nn7.

%e If n=6, 7nn7 is 7667.

%e If n=15, 7nn7 is 715157 (a prime)

%e If n=18, 7nn7 is 718187 (a prime)

%e If n=19, 7nn7 is 719197 (a prime)

%p a:= n-> parse(cat(7,n,n,7)):

%p seq(a(n), n=0..35); # _Alois P. Heinz_, Jan 24 2020

%t Table[idn=IntegerDigits[n];FromDigits[Join[{7},idn,idn,{7}]],{n,0,30}] (* _Harvey P. Dale_, May 14 2013 *)

%Y Cf. A100846.

%K nonn,base,easy

%O 0,1

%A _Parthasarathy Nambi_, Jan 10 2005

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Last modified January 23 14:29 EST 2022. Contains 350512 sequences. (Running on oeis4.)