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Sum of decimal digits of two successive natural numbers.
1

%I #19 Sep 08 2019 18:59:18

%S 1,3,5,7,9,11,13,15,17,10,3,5,7,9,11,13,15,17,19,12,5,7,9,11,13,15,17,

%T 19,21,14,7,9,11,13,15,17,19,21,23,16,9,11,13,15,17,19,21,23,25,18,11,

%U 13,15,17,19,21,23,25,27,20,13,15,17,19,21,23,25,27,29,22,15,17,19,21,23

%N Sum of decimal digits of two successive natural numbers.

%H Jason Jewell, <a href="/A118137/b118137.txt">Table of n, a(n) for n = 0..1000</a> (first 75 terms from Giovanni Teofilatto)

%F a(n) = A007953(n) + A007953(n+1). - _Michel Marcus_, Sep 06 2019

%p read("transforms") ;

%p A118137 := proc(n)

%p digsum(n)+digsum(n+1) ;

%p end proc: # _R. J. Mathar_, Apr 03 2012

%p # second Maple program:

%p a:= n-> add(i, i=convert(parse(cat(n, n+1)), base, 10)):

%p seq(a(n), n=0..100); # _Alois P. Heinz_, Sep 08 2019

%t a[n_] := Total@ Flatten@ IntegerDigits[{n, n+1}]; Array[a, 80, 0] (* _Giovanni Resta_, Sep 06 2019 *)

%o (PARI) a(n) = sumdigits(n) + sumdigits(n+1); \\ _Michel Marcus_, Sep 06 2019

%Y Cf. A007953.

%K base,easy,nonn

%O 0,2

%A _Giovanni Teofilatto_, May 13 2006

%E Added missing term a(18). - _Jason Jewell_, Sep 06 2019