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Positions n of digits "1" in the concatenated terms of A210538 for which A210538(n) is not prime.
1

%I #13 Apr 14 2022 03:12:28

%S 1,10,19,22,28,34,187,197,210,220,232,247,250,253,256,262,280,286,289,

%T 307,318,321,329,332,353,358,361,364,383,413,426,445,451,453,462,472,

%U 484,490,512,523,532,538,559,572,577,579,586,597,635,644,723,809,882,930,941,1020

%N Positions n of digits "1" in the concatenated terms of A210538 for which A210538(n) is not prime.

%C Primes > 7 occur in A210538 at indices n corresponding to digits "1" in the concatenation of the terms. This sequence lists counterexamples for which the converse is not true, i.e., position of digits "1" not corresponding to primes.

%C Note the irregular distribution: there are no terms between 34 and 187, but then many terms up to 597. These are followed by only 7 terms preceding 1020, which starts a series of 6 terms up to 1140.

%e a(1)=1 because the 1st digit of A210538 is "1", but A210538(1)=1 is not prime.

%e a(2)=10, because the 10th digit of A210538 is "1", but A210538(10)=10 is not prime.

%Y Cf. A210538.

%K nonn,base

%O 1,2

%A _M. F. Hasler_, Mar 22 2012