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A123928 Numbers k such that the sum of the first k primes with the final digit 1 is prime (the number of consecutive prime numbers in A030430 that should be added to obtain A129077(x)).

%I A123928 #11 Jul 17 2025 21:45:22
%S A123928 1,3,11,27,29,31,33,49,73,77,79,123,149,157,167,169,189,207,211,219,
%T A123928 223,227,241,261,313,319,323,329,333,357,359,417,419,423,441,463,477,
%U A123928 491,499,513,517,553,559,573,637,667,707,709,711,729,747,757,777,813,893
%N A123928 Numbers k such that the sum of the first k primes with the final digit 1 is prime (the number of consecutive prime numbers in A030430 that should be added to obtain A129077(x)).
%H A123928 Harvey P. Dale, <a href="/A123928/b123928.txt">Table of n, a(n) for n = 1..1000</a>
%F A123928 a(n)=primes in A030430 added to obtain A129077(n)
%e A123928 a(3)=11 because 11 is the number of consecutive prime numbers in A030430 that must be added to obtain A129077(3).
%t A123928 Position[Accumulate[Select[Prime[Range[5000]],Mod[#,10]==1&]],_?PrimeQ]//Flatten (* _Harvey P. Dale_, May 21 2023 *)
%Y A123928 Cf. A030430; A129077; A129078; A129079; A129081; A000040.
%K A123928 easy,base,nonn,less
%O A123928 1,2
%A A123928 _Tomas Xordan_, May 13 2007