A257244 - OEIS

%I #13 May 06 2015 09:26:34

%S 2,2,3,3,3,3,3,3,3,3,5,5,5,3,3,3,3,3,5,5,7,7,7,7,7,3,3,3,19,7,7,3,5,5,

%T 5,3,7,5,5,5,19,11,11,3,13,13,13,3,23,13,13,5,11,11,11,3,61,7,31,3,13,

%U 13,19,3,43,13,13,3,7,5,5,5,61,11,31,23,23,3,127,7,7,3,151,7,19,3,181,7,13,3,43,31,31

%N First differences of A256393: a(n) = A256393(n+1) - A256393(n).

%C Sequence gives the differences between the successive terms of A256393, each difference being equal to their unique shared prime factor.

%H Antti Karttunen, <a href="/A257244/b257244.txt">Table of n, a(n) for n = 1..4095</a>

%F a(n) = A256393(n+1) - A256393(n).

%F a(n) = gcd(A256393(n+1), A256393(n)).

%t f[n_] := Block[{pf = First /@ FactorInteger@ n},

%t   If[EvenQ@ n, Max@ pf, Min@ pf]]; s = {2}; lmt = 94; For[k = 2,

%t k <= lmt, k++, AppendTo[s, s[[k - 1]] + f@ s[[k - 1]]]]; Abs[

%t Subtract @@@ Partition[s, 2, 1]] (* _Michael De Vlieger_, Apr 19 2015 *)

%o (Scheme, two alternatives)

%o (define (A257244 n) (- (A256393 (+ n 1)) (A256393 n)))

%o (define (A257244 n) (gcd (A256393 (+ n 1)) (A256393 n)))

%o (Haskell)

%o a257244 n = a257244_list !! (n-1)

%o a257244_list = zipWith gcd a256393_list $ tail a256393_list

%o -- _Reinhard Zumkeller_, May 06 2015

%Y Cf. A257245, A257246 (bisections), A257247 (positions where they coincide).

%Y Cf. A256393.

%K nonn

%O 1,1

%A _Antti Karttunen_, Apr 19 2015