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 A053999 Prime number spiral (clockwise, Northwest spoke). 9
 2, 23, 97, 227, 419, 661, 1009, 1427, 1879, 2437, 3083, 3803, 4637, 5519, 6481, 7573, 8737, 9931, 11321, 12743, 14327, 15877, 17609, 19471, 21391, 23327, 25469, 27739, 30047, 32429, 34849, 37501, 40231, 42943, 45989, 49037, 52121, 55381, 58579 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Largest prime in n-th shell of prime spiral. Shell 1 comprises the primes 3 5 7 11 13 17 19 23; 3 is lowest, 23 is highest. LINKS Ivan Panchenko, Table of n, a(n) for n = 0..1000 FORMULA 8-spoke wheel overlays prime number spiral; hub is 2 in shell 0; 8 spokes radiate from this hub; this is Northwest, clockwise. a(n) = A000040(A016754(n)) . - R. J. Mathar, Aug 29 2018 EXAMPLE Begin a prime number spiral at shell 0 (prime 2), proceed clockwise, Northwest. From Omar E. Pol, Feb 19 2022: (Start) The spiral with four terms in every spoke looks like this: . 227 101--103--107--109--113--127 | | | 223 97 29---31---37---41 131 | | | | | 211 89 23 3----5 43 137 | | | | | | | 199 83 19 2 7 47 139 | | | | | | 197 79 17---13---11 53 149 | | | | 193 73---71---67---61---59 151 | | 191--181--179--173--167--163--157 . (End) MATHEMATICA Table[ Prime[4n^2 + 4n + 1], {n, 0, 40} ] CROSSREFS Cf. A016754, A054551, A054553, A054555, A054564, A054566, A054566, A054570. Sequence in context: A270868 A239186 A238185 * A357739 A131176 A141405 Adjacent sequences: A053996 A053997 A053998 * A054000 A054001 A054002 KEYWORD easy,nonn AUTHOR Enoch Haga and G. L. Honaker, Jr., Apr 10 2000 EXTENSIONS Edited by Robert G. Wilson v, Feb 25 2002 STATUS approved

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Last modified February 21 03:04 EST 2024. Contains 370219 sequences. (Running on oeis4.)