OFFSET
1,2
COMMENTS
In case the sequence b is not a permutation of natural numbers, then neither this will be and we set a(n) = -1 for those n > 1 that do not occur in A257906.
LINKS
PROG
(Scheme, with macro defineperm1 from Antti Karttunen's IntSeq-library)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 20 2015
STATUS
approved