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 A330434 a(1) = 1, a(2) = 2; thereafter a(n) = smallest number not occurring earlier such that the sum of three successive digits is prime. 1
 1, 2, 4, 5, 8, 6, 3, 20, 9, 22, 7, 24, 10, 11, 13, 17, 31, 15, 51, 19, 35, 33, 53, 37, 39, 55, 71, 57, 73, 77, 91, 75, 59, 95, 93, 79, 110, 12, 21, 28, 14, 25, 42, 18, 23, 26, 32, 27, 40, 16, 41, 60, 50, 29, 62, 30, 43, 44, 34, 45, 48, 54, 49, 46, 38, 63, 80, 52, 47, 64, 36, 83, 68, 56, 61, 66, 58, 65, 84, 70, 67, 401 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Carole Dubois, Table of n, a(n) for n = 1..508 EXAMPLE After 8 and 6 the next term is 3 as 8+6+3 = 17 is a prime; After 6 and 3 the next term is 20 as 6+3+2 = 11 and 3+2+0 = 5 are primes; After 20 the next term is 9 as 2+0+9 = 11 is a prime; etc. MATHEMATICA Nest[Append[#, Block[{k = 3}, While[Nand[FreeQ[#, k], AllTrue[Table[Total@ #[[i ;; i + 2]], {i, Length@ # - 2}], PrimeQ] &@ Flatten@ IntegerDigits@ Append[#, k] ], k++]; k]] &, {1, 2}, 80] (* Michael De Vlieger, Dec 14 2019 *) CROSSREFS Cf. A076990 (3 successive terms have a prime sum), A330424 (3 successive terms AND 3 successive digits have a prime sum). Sequence in context: A262942 A352808 A076990 * A330424 A057168 A087711 Adjacent sequences: A330431 A330432 A330433 * A330435 A330436 A330437 KEYWORD base,nonn AUTHOR Eric Angelini and Carole Dubois, Dec 14 2019 STATUS approved

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Last modified August 14 18:55 EDT 2024. Contains 375166 sequences. (Running on oeis4.)