A260093 Numbers n for which A259124(n) = A259124(n-1) + 1.

20, 49, 2096, 5684, 14847, 440876, 18770091, 40882585915, 5598199195808, 35959924244180

Offset

1,1

Comments

Is the sequence infinite?

a(11) > 5 * 10^13. - Hiroaki Yamanouchi, Aug 24 2015

Links

Table of n, a(n) for n=1..10.

Prog

(Python)
TOP = 5000*5000
a = [0]*TOP
for y in range(2, 5000):
  z = TOP//y + 1
  for x in range(y, z):
    n = x*y + x + y
    if n>=TOP: break
    a[n] += x+y
for n in range(1, TOP):
    if a[n]==a[n-1]+1 and a[n]>0: print(n, end=', ')
(PARI) a259124(n)=sum(y=2, sqrtint(n+1)-1, my(x=(n-y)/(y+1)); if(denominator(x)==1, x+y));
isok(n)= a259124(n) == a259124(n-1) + 1; \\ Michel Marcus, Aug 05 2015

Crossrefs

Cf. A259124, A259432.

Sequence in context: A115882 A303295 A277553 * A304832 A007589 A182462

Adjacent sequences: A260090 A260091 A260092 * A260094 A260095 A260096

Keyword

nonn,more,changed

Author

Alex Ratushnyak, Jul 15 2015

Extensions

a(8)-a(9) from Hiroaki Yamanouchi, Aug 24 2015

a(10) from Hiroaki Yamanouchi, Aug 25 2015

Status

approved