A194080 Partial sums of the squarefree integers that are triangular.

1, 3, 6, 45, 2775, 239778, 3293461, 3815703, 8142176137578, 25025955346953, 27262684236385, 2430563686654005, 17543349622599580, 95966329187365806, 69152680331115315990, 130831703828369011153, 10553338813847920825078, 120456843371021570368956

Offset

1,2

Comments

For the partial sum to the squarefree integer: 1, 2, 3, 11, 94, 890, 3290, 3538, 5175587, 9073717, 9470490, 89421695, 240240143, ..., .

No more terms in the first 4*10^11 partial sums. - Donovan Johnson, Feb 20 2012

Links

Table of n, a(n) for n=1..18.

Mathematica

triQ[n_] := IntegerQ@ Sqrt[ 8n + 1]; k = 1; s = 0; lst = {}; While[k < 3*10^8, If[ SquareFreeQ@ k, s = s + k; If[ triQ@ s, AppendTo[lst, s]; Print[{k, s}]]]; k++]

Crossrefs

Cf. A005117, A173143.

Sequence in context: A076170 A137775 A038050 * A261841 A197884 A279706

Adjacent sequences: A194077 A194078 A194079 * A194081 A194082 A194083

Keyword

nonn

Author

Robert G. Wilson v, Aug 19 2011

Extensions

a(14)-a(16) from Donovan Johnson, Aug 24 2011

a(17)-a(18) from Donovan Johnson, Feb 20 2012

Status

approved