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 A227950 Number of decimal digits in the increasing sequence of primes obtainable by concatenating successive decrements from some power of 10. 2
 3, 5, 5, 7, 9, 11, 13, 13, 15, 17, 19, 21, 25, 27, 53, 81, 85, 183, 191, 307, 377, 409, 475, 541, 565, 885, 1065, 1399, 1489, 2653, 4523, 4565, 5773, 7777, 14281 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Any even value necessarily involves crossing through an entire string of numbers of the same length (10^k-1 to 10^(k-1)).  Since primes of this kind do not arise for any leading power of 10 less than 5, finding such a number is unlikely using current hardware and software tools. LINKS EXAMPLE 1000999998997 is one of the primes described and provides a value of 13 in this sequence, with 1000000999999 providing the other (A227949(7) and A227949(8), in opposite order for the purposes of the FORMULA at that sequence (technically)). CROSSREFS Cf. A227949,A227951 Sequence in context: A219844 A168056 A122800 * A063202 A058020 A069201 Adjacent sequences:  A227947 A227948 A227949 * A227951 A227952 A227953 KEYWORD nonn,base AUTHOR James G. Merickel, Aug 22 2013 STATUS approved

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Last modified September 30 02:48 EDT 2020. Contains 337432 sequences. (Running on oeis4.)