1,2

n+1 first appears in the sequence at the A002522(n)-th entry (since the ultimate occurrence of n is n^2). a(n) refers to the greatest minimal length of monotone subsequence (i.e.either increasing or decreasing) contained within any sequence of n distinct numbers,according to the Erdos-Szekeres theorem - Lekraj Beedassy (blekraj(AT)yahoo.com), May 20 2003

M. Somos, Sequences used for indexing triangular or square arrays

a(n) = ceiling(sqrt(n)).

G.f.: (Sum_{n>=0} x^(n^2))x/(1-x). - Michael Somos, May 03, 2003

(PARI) a(n)=if(n<1, 0, 1+sqrtint(n-1))

Sequence in context: A083375 A088519 A135034 this_sequence A011752 A025790 A030617

Adjacent sequences: A003056 A003057 A003058 this_sequence A003060 A003061 A003062

nonn,easy

njas