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A112958 a(1) = a(2) = a(3) = a(4) = 1; for n>1: a(n+4) = a(n)^2 + a(n+1)^2 + a(n+2)^2 + a(n+3)^2. 6

%I #12 Aug 21 2016 04:09:07

%S 1,1,1,1,4,19,379,144019,20741616379,430214650034342688004,

%T 185084645104171955001009752069374428191659

%N a(1) = a(2) = a(3) = a(4) = 1; for n>1: a(n+4) = a(n)^2 + a(n+1)^2 + a(n+2)^2 + a(n+3)^2.

%C A quadratic tetranacci sequence.

%C This is to A000283 as a tetranacci (A000288) is to Fibonacci. Primes in this begin 19, 379.

%H Seiichi Manyama, <a href="/A112958/b112958.txt">Table of n, a(n) for n = 1..15</a>

%e 1^2 + 4^2 + 19^2 + 379^2 = 144019.

%t RecurrenceTable[{a[1] == a[2] == a[3] == a[4] == 1, a[n] == a[n-1]^2 + a[n-2]^2 + a[n-3]^2 + a[n-4]^2}, a, {n, 15}] (* _Vincenzo Librandi_, Aug 21 2016 *)

%Y Cf. A000283, A000288, A112957, A112959, A112960.

%K easy,nonn

%O 1,5

%A _Jonathan Vos Post_, Jan 02 2006

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Last modified March 28 12:26 EDT 2024. Contains 371254 sequences. (Running on oeis4.)