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Number of odd digits in the concatenation of first n primes.
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%I #12 Jul 16 2018 09:13:52

%S 0,1,2,3,5,7,9,11,12,13,15,17,18,19,20,22,24,25,26,28,30,32,33,34,36,

%T 38,40,42,44,47,49,52,55,58,60,63,66,68,70,73,76,78,81,84,87,90,92,93,

%U 94,95,97,99,100,102,104,105,106,108,110,111,112,114,116,119,122,125,128

%N Number of odd digits in the concatenation of first n primes.

%C Partial sums of A104638. [_R. J. Mathar_, Feb 13 2009]

%H Robert Israel, <a href="/A155498/b155498.txt">Table of n, a(n) for n = 1..10000</a>

%e If n=1, concatenate first 1 prime = 2, then number of odd digits = 0 = a(1).

%e If n=2, concatenate first 2 primes = 23, then number of odd digits = 1 = a(2).

%e If n=3, concatenate first 3 primes = 235, then number of odd digits = 2 = a(3).

%p ListTools:-PartialSums([seq(nops(select(type, convert(ithprime(i), base, 10), odd)), i=1..100)]); # _Robert Israel_, Jul 15 2018

%o (PARI) a(n) = sum(k=1, n, #select(x->(x%2), digits(prime(k)))); \\ _Michel Marcus_, Jul 16 2018

%Y Cf. A000040, A068670.

%K nonn,base

%O 1,3

%A _Juri-Stepan Gerasimov_, Jan 23 2009

%E Replaced 53 by 55. _R. J. Mathar_, Feb 13 2009