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 A234965 Numbers n such that 123...n - (n+1) is prime. 0
 4, 6, 10, 12, 63, 270, 466, 898, 1647 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(10) > 2600. - Giovanni Resta, Jan 11 2014 LINKS Table of n, a(n) for n=1..9. EXAMPLE 1234 - 5 = 1229 is prime so 4 is a member of this sequence. 123456 - 7 = 123449 is prime so 6 is a member of this sequence. MATHEMATICA c = 0; Do[c = n + c*10^IntegerLength[n]; If[PrimeQ[c-n-1)], Print@n], {n, 1700}] (* Giovanni Resta, Jan 11 2014 *) PROG (Python) def Concatenate(x): ..num = '' ..for n in range(1, x+1): ....num += str(n) ..return int(num) import sympy from sympy import isprime {print(x) for x in range(1, 10**3) if isprime(Concatenate(x)-(x+1))} CROSSREFS Cf. A234964, A007908. Sequence in context: A310582 A177929 A086493 * A320881 A224796 A190370 Adjacent sequences: A234962 A234963 A234964 * A234966 A234967 A234968 KEYWORD nonn,base,more AUTHOR Derek Orr, Jan 02 2014 EXTENSIONS a(9) from Giovanni Resta, Jan 11 2014 STATUS approved

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Last modified May 21 12:09 EDT 2024. Contains 372736 sequences. (Running on oeis4.)