

A052380


a(n) = D is the smallest distance (D) between 2 nonoverlapping prime twins differing by d=2n; these twins are [p,p+d] or [p+D,p+D+d] and p > 3.


17



6, 6, 6, 12, 12, 12, 18, 18, 18, 24, 24, 24, 30, 30, 30, 36, 36, 36, 42, 42, 42, 48, 48, 48, 54, 54, 54, 60, 60, 60, 66, 66, 66, 72, 72, 72, 78, 78, 78, 84, 84, 84, 90, 90, 90, 96, 96, 96, 102, 102, 102, 108, 108, 108, 114, 114, 114, 120, 120, 120, 126, 126, 126, 132
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OFFSET

1,1


COMMENTS

For d=D the quadruple of primes becomes a triple: [p,p+d],[p+d,p+2d].
Without the p > 3 condition, a(1)=2.
The starter prime p, is followed by a prime dpattern of [d,Dd,d], where Dd=a(n)2n is 4,2 or 0; these dpatterns are as follows: [2,4,2], [4,2,4], [6,6], [8,4,8], [10,2,10], [12,12], etc.
All terms of this sequence have digital root 3, 6 or 9.  J. W. Helkenberg, Jul 24 2013
a(n+1) is also the number of the circles added at the nth iteration of the pattern generated by the construction rules: (i) At n = 0, there are six circles of radius s with centers at the vertices of a regular hexagon of side length s. (ii) At n > 0, draw a circle with center at each boundary intersection point of the figure of the previous iteration. The pattern seems to be the flower of life except at the central area. See illustration.  Kival Ngaokrajang, Oct 23 2015


LINKS

Table of n, a(n) for n=1..64.
Kival Ngaokrajang, Illustration of initial terms
Sacred Geometry, Flower of life


FORMULA

a(n) = 6*ceiling(n/3) = 6*ceiling(d/6) = D = D(n).
a(n) = 2n + 4  2((n+2) mod 3).  Wesley Ivan Hurt, Jun 30 2013
a(n) = 6*A008620(n1).  Kival Ngaokrajang, Oct 23 2015


EXAMPLE

n=5, d=2n=10, the minimal distance for 10twins is 12 (see A031928, d=10) the smallest term in A053323. It occurs first between twins of [409,419] and [421,431]; see 409 = A052354(1) = A052376(1) = A052381(5).


MATHEMATICA

Table[2 n + 4  2 Mod[n + 2, 3], {n, 66}] (* Michael De Vlieger, Oct 23 2015 *)


PROG

(PARI) vector(200, n, n; 6*(n\3+1)) \\ Altug Alkan, Oct 23 2015


CROSSREFS

Cf. A001223, A031924A031938, A053319A053331, A052350A052358, A008620.
Sequence in context: A035019 A216057 A212096 * A315826 A304821 A315827
Adjacent sequences: A052377 A052378 A052379 * A052381 A052382 A052383


KEYWORD

nonn,easy


AUTHOR

Labos Elemer, Mar 13 2000


STATUS

approved



