A187086 -id:A187086 - cp's OEIS frontend

A187095 Numbers n such that n and n+1 are terms in A187086.

39, 291, 2158, 10083, 22178, 60483, 108291, 129382, 235138, 266403, 288291, 311043, 367491, 410691, 524163, 561478, 608158, 662691, 1563843, 1713717, 2007363, 3126058, 3512163, 3573778

Offset: 1

Zak Seidov, Mar 04 2011

nonn

Cf. A187086.

A187087 Positive squares in the order of their appearance in A048050.

Original entry on oeis.org

9, 16, 49, 25, 16, 49, 64, 121, 36, 81, 64, 169, 36, 225, 100, 225, 64, 36, 441, 36, 169, 361, 225, 144, 441, 441, 144, 256, 400, 196, 64, 441, 144, 361, 64, 400, 441, 729, 961, 64, 196, 144, 729, 100, 841, 729, 400, 256, 1225, 100, 729, 1225, 961, 900, 841

Offset: 1

Zak Seidov, Mar 04 2011

nonn

Corresponding values of n are in A187086. A048050 is Chowla's function: sum of divisors of n except 1 and n.

By the Goldbach conjecture, every even square appears; take two odd primes p and q such that p+q = k^2, then Chowla function of p*q is k^2. It appears that 17^2 is the first odd square not in A048050.

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A048050, A187086.

A048050:=func< n | n eq 1 or IsPrime(n) select 0 else &+[ a: a in Divisors(n) | a ne 1 and a ne n ] >; [ a: n in [1..2500] | a gt 0 and IsSquare(a) where a is A048050(n) ]; // Klaus Brockhaus, Mar 04 2011

chowla[n_] := DivisorSigma[1, n] - n - 1; s = {}; Do[c = chowla[n]; If[c > 0 && IntegerQ@Sqrt[c], AppendTo[s, c]], {n, 1, 10^3}]; s (* Amiram Eldar, Aug 28 2019 *)

{for(n=1,2000,spf=sumdiv(n,x,x)-1-n;if(spf>0&&issquare(spf),print1(spf",")))}

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A187095 Numbers n such that n and n+1 are terms in A187086.

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A187087 Positive squares in the order of their appearance in A048050.

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