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 A069048 Numbers n such that n is a concatenation of consecutive natural numbers, starting from 1 and n+1 is prime. 0
 12, 123456, 123456789101112131415161718192021222324252627282930, 123456789101112131415161718192021222324252627282930313233343536373839404142434, 445464748495051525354555657585960616263646566676869707172737475767778798081828 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Let n be a concatenation of consecutive natural numbers, starting from 1. Is n ever a prime number? LINKS EXAMPLE 123456 is a concatenation, starting with 1, of consecutive natural numbers and 123456 + 1 is prime. MATHEMATICA z = {1}; For[i = 2, i <= 100, i++, z = Flatten[Append[z, IntegerDigits[i]]]; y = FromDigits[z]; If[PrimeQ[y + 1], Print[y]]] CROSSREFS Sequence in context: A056540 A331093 A328992 * A284287 A100246 A055323 Adjacent sequences:  A069045 A069046 A069047 * A069049 A069050 A069051 KEYWORD base,nonn AUTHOR Joseph L. Pe, Apr 03 2002 STATUS approved

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Last modified September 20 22:20 EDT 2021. Contains 347596 sequences. (Running on oeis4.)