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A258767
With a(1) = 1, a(n) is the smallest number not already in the sequence such that a(n)^2 + a(n-1)^2 is not squarefree.
3
1, 7, 14, 2, 4, 3, 6, 8, 10, 5, 12, 9, 13, 16, 18, 15, 20, 21, 22, 11, 23, 36, 24, 26, 28, 29, 47, 46, 30, 25, 35, 40, 32, 34, 17, 19, 33, 27, 31, 42, 38, 41, 37, 39, 45, 48, 44, 50, 49, 43, 51, 54, 52, 56, 58, 59, 62, 60, 55, 65, 70, 63, 57, 66, 64, 68, 72, 69, 67, 81, 75, 78, 71, 53, 79, 97, 96, 74
OFFSET
1,2
COMMENTS
Believed to be a permutation of the natural numbers.
LINKS
PROG
(PARI) v=[1]; n=1; while(n<100, if(!issquarefree(n^2+v[#v]^2)&&!vecsearch(vecsort(v), n), v=concat(v, n); n=0); n++); v
(Haskell)
import Data.List (delete)
a258767 n = a258767_list !! (n-1)
a258767_list = 1 : f 1 [2..] where
f x zs = g zs where
g (y:ys) | a008966 (x^2 + y^2) == 1 = g ys
| otherwise = y : f y (delete y zs)
-- Reinhard Zumkeller, Jun 11 2015
CROSSREFS
Cf. A258768 (fixed points).
Cf. A008966, A258827 (putative inverse).
Sequence in context: A227173 A178998 A188929 * A169845 A302972 A115146
KEYWORD
nonn
AUTHOR
Derek Orr, Jun 09 2015
STATUS
approved