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 A301943 Number of primes of the form b^2+1 for b <= 10^n that end in 1. 2
 1, 4, 42, 279, 2236, 18155, 152020, 1317648, 11634451, 104116591, 942191087 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA a(n) + A301944(n) + 2 = A206709(n). EXAMPLE 101, 401, 1601 and 8101 are primes; so a(2) = 4. MATHEMATICA c = k = 0; lst = {}; Do[ While[k <= 10^n, If[ PrimeQ[k^2 + 1], c++]; k+=10]; AppendTo[lst, c]; Print[c], {n, 9}] (* Robert G. Wilson v, Mar 30 2018 *) PROG (Python) from sympy import isprime def A301943(n):     return sum(1 for i in range(1, 10**(n-1)+1) if isprime(100*i**2+1)) # Chai Wah Wu, Mar 30 2018 CROSSREFS Cf. A002496, A206709, A301944. Sequence in context: A220835 A157719 A280956 * A219101 A118447 A219980 Adjacent sequences:  A301940 A301941 A301942 * A301944 A301945 A301946 KEYWORD nonn,more,base AUTHOR Seiichi Manyama, Mar 29 2018 EXTENSIONS a(10) from Robert G. Wilson v, Mar 31 2018 a(11) from Robert G. Wilson v, Apr 04 2018 STATUS approved

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Last modified December 6 06:14 EST 2021. Contains 349563 sequences. (Running on oeis4.)