A045800 - OEIS

%I #26 Mar 16 2023 08:50:40

%S 1,7,43,49,101,107,143,149,201,207,243,249,301,307,343,349,401,407,

%T 443,449,501,507,543,549,601,607,643,649,701,707,743,749,801,807,843,

%U 849,901,907,943,949,1001,1007,1043,1049,1101,1107,1143,1149,1201,1207

%N 0-ish numbers (end in 01, 07, 43, 49).

%H Reinhard Zumkeller, <a href="/A045800/b045800.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,1,-1).

%F G.f.: x*(1+6*x+36*x^2+6*x^3+51*x^4)/(1-x-x^4+x^5). - _Colin Barker_, Jan 23 2012

%F a(n) = (50*n-8*i^(n*(n+1))-19*(-1)^n-75)/2, where i=sqrt(-1). - _Bruno Berselli_, Feb 22 2012

%t LinearRecurrence[{1,0,0,1,-1},{1,7,43,49,101},60] (* _Harvey P. Dale_, Jul 26 2015 *)

%o (Haskell)

%o import Data.List (findIndices)

%o a045800 n = a045800_list !! (n-1)

%o a045800_list = findIndices (`elem` [1,7,43,49]) $ cycle [0..99]

%o -- _Reinhard Zumkeller_, Jan 23 2012

%Y Cf. A045801-A045809, A045572, A045797, A045798.

%K nonn,base,easy

%O 1,2

%A _J. H. Conway_.

%E More terms from _Erich Friedman_.