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A059428 Number of points of rotation in a prime block spiral. 1

%I

%S 2,3,5,11,17,29,41,59,73,101,127,157,191,229,269,313,367,421,467,547,

%T 607,673,751,829,919,1013,1093,1201,1297,1429,1523,1621,1753,1889,

%U 2027,2153,2309,2441,2621,2749,2909,3089,3299,3463,3623,3821,4007,4217,4421

%N Number of points of rotation in a prime block spiral.

%C Analogous to A002620 except primes are substituted for the natural numbers.

%F Arrange primes in a block spiral formation. a(n) is determined by the point of rotation to allow for continuation of the sequence.

%e Spiral begins:

%e (73)-79--83--89--97-(101)

%e | |

%e 71 (17)-19--23-(29) etc.

%e | | |

%e 67 13 (2)-(3) 31

%e | | | |

%e 61 (11)--7--(5) 37

%e | |

%e (59)-53--47--43-(41)

%p A059428 := proc(n) RETURN(ithprime(1+floor(n^2/4))) end: # Francisco Salinas (franciscodesalinas(AT)hotmail.com), Jan 05 2002

%K easy,nonn

%O 1,1

%A _Jason Earls_, Mar 15 2001

%E More terms from Larry Reeves (larryr(AT)acm.org), Apr 19 2001

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Last modified October 27 13:45 EDT 2021. Contains 348276 sequences. (Running on oeis4.)