A062918 - OEIS

%I #33 Dec 25 2021 11:05:04

%S 1,3,6,10,15,21,28,36,45,46,57,78,109,150,201,262,333,414,505,507,519,

%T 541,573,615,667,729,801,883,975,978,991,1014,1047,1090,1143,1206,

%U 1279,1362,1455,1459,1473,1497,1531,1575,1629,1693,1767,1851,1945,1950,1965

%N Sum of the digit reversals of the first n natural numbers.

%C a(n) = A000217(n) for n=1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 86, 89, ...; checked up to 10^7. - _Michel Marcus_, Sep 15 2015; checked up to 2^32 ~ 4*10^9. - _Kenny Lau_, Aug 01 2017

%H Harry J. Smith, <a href="/A062918/b062918.txt">Table of n, a(n) for n=1..1000</a>

%e a(12) = 78 as 1+2+3+4+5+6+7+8+9+R(10)+R(11)+R(12) = 1+2+3+4+5+6+7+8+9+01+11+21 = 78.

%t Accumulate[Table[FromDigits[Reverse[IntegerDigits[n]]],{n,1,120}]] (* _Enrique Pérez Herrero_, Jun 01 2013 *)

%t Accumulate[IntegerReverse[Range[60]]] (* _Harvey P. Dale_, Dec 25 2021 *)

%o (PARI) { a=0; for (n=1, 1000, x=n; r=0; while (x>0, d=x-10*(x\10); x\=10; r=r*10 + d); write("b062918.txt", n, " ", a+=r) ) } \\ _Harry J. Smith_, Aug 12 2009

%o (PARI) a(n) = sum(k=1,n, eval(concat(Vecrev(Str(k))))); \\ _Michel Marcus_, Sep 15 2015

%Y Cf. A000217, A004086, A069792.

%K nonn,base,easy

%O 1,2

%A _Amarnath Murthy_, Jul 02 2001

%E More terms from Larry Reeves (larryr(AT)acm.org), Jul 05 2001