

A202025


Position of second appearance of set of first n terms in the sequence of odd primes modulo 4.


0



3, 4, 8, 16, 16, 19, 60, 221, 654, 654, 654, 654, 654, 30291, 30291, 30291, 30291, 250231, 342916, 342916, 472727, 1934365, 1934365, 11877702, 11877702, 11877702
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OFFSET

1,1


COMMENTS

Next term, a(27) > 3*10^7.


LINKS

Table of n, a(n) for n=1..26.


EXAMPLE

Consider the sequence of odd primes modulo 4: S= 3, 1, 3, 3, 1, 1, 3, 3, 1, 3, 1, 1, 3, 3, 1, 3, 1,... . Then
a(1)=3 because 2nd appearance of 3 is S(3),
a(2)=4 because 2nd appearance of (3,1) begins at S(4),
a(3)=8 because 2nd appearance of (3,1,3) begins at S(8),
a(4)=16 because 2nd appearance of (3,1,3,3) begins at S(16).


MATHEMATICA

nn=3*10^7; s=Table[Mod[Prime[n], 4], {n, 2, nn}]; Reap[k1=2; Do[tn=Take[s, n]; Do[If[tn==Take[s, {k, k+n1}], Sow[k]; k1=k; Break[]], {k, k1, nnn1}], {n, 26}]][[2, 1]]


CROSSREFS

Cf. A039702.
Sequence in context: A027977 A165438 A293781 * A227615 A049894 A198633
Adjacent sequences: A202022 A202023 A202024 * A202026 A202027 A202028


KEYWORD

nonn


AUTHOR

Zak Seidov, Dec 09 2011


STATUS

approved



