A027924 a(n) = least k such that 1+2+...+k >= 1^3 + 2^3 + ... + n^3.

1, 4, 8, 14, 21, 30, 40, 51, 64, 78, 93, 110, 129, 148, 170, 192, 216, 242, 269, 297, 327, 358, 390, 424, 460, 496, 535, 574, 615, 658, 701, 747, 793, 841, 891, 942, 994, 1048, 1103, 1160, 1218, 1277, 1338, 1400, 1464, 1529, 1595, 1663, 1732, 1803, 1875

Offset

1,2

Links

Table of n, a(n) for n=1..51.

Formula

a(n) = round(sqrt(1/2)*n*(n+1)). - Ralf Stephan, Jan 24 2003

Prog

(PARI) for(n=1, 100, print1(round(sqrt(1/2)*n*(n+1))", ")).
(Python)
from math import isqrt
def A027924(n): return isqrt((n*(n+1))**2<<1)+1>>1 # Chai Wah Wu, Jun 19 2024

Crossrefs

Cf. A000537.

Sequence in context: A088804 A374505 A344012 * A006578 A122224 A183955

Adjacent sequences: A027921 A027922 A027923 * A027925 A027926 A027927

Keyword

nonn

Author

Clark Kimberling

Extensions

More terms from Ralf Stephan, Jan 24 2003

Status

approved