

A086409


a[1]=1; a[n+1]=a[n]1 if (prime[a[n]]+1)/2 is even, else a[n+1]=a[n]+4.


3



1, 5, 4, 3, 7, 11, 10, 14, 13, 17, 16, 20, 19, 18, 22, 21, 25, 29, 33, 37, 41, 40, 44, 48, 47, 46, 45, 49, 48, 47, 46, 45, 49, 48, 47, 46, 45, 49, 48, 47, 46, 45, 49, 48, 47, 46, 45, 49, 48, 47, 46
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OFFSET

1,2


COMMENTS

There is a cycle starting with a(26)=46: ...46,45,49,48,47,46,...


LINKS



EXAMPLE

a(3)=4 because a(2)=5, prime[5]=11 (11+1)/2 is even and a(3)=a(2)1


MATHEMATICA

b=1; Prepend[Table[b+=If[EvenQ[(Prime[b]+1)/2], 1, 4], {i, 52}], 1] (*A086409*)
NestList[If[EvenQ[(Prime[#]+1)/2], #1, #+4]&, 1, 50] (* Harvey P. Dale, Mar 05 2020 *)


CROSSREFS



KEYWORD

easy,nonn


AUTHOR



STATUS

approved



