A376941 Lexicographically earliest sequence of positive integers a(1), a(2), a(3), ... such that for any n > 0, Sum_{k = 1..n} 1/(k*a(k)) < Sum_{k = 1..oo} 1/k^2 = Pi^2/6.

1, 1, 3, 8, 78, 18826, 848809436, 3078251288697343844, 37949774653961921717972183675013581047, 4221065664206126654046840821317530741151656832301121739091602085731664210467

Offset

1,3

Links

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

Example

a(7) = 848809436 as Sum_{k = 1..7} 1/(k*a(k)) = 1/(1*1) + 1/(2*1) + ... + 1/(6*18826) + 1/(7*848809436) = 430556991329920237/261747263922187680, which is ~4.1*10^-20 less than Pi^2/6.

Crossrefs

Cf. A013661, A376934, A270744, A375781, A375529, A074631, A270752.

Sequence in context: A208817 A356529 A060752 * A347641 A287389 A233175

Adjacent sequences: A376938 A376939 A376940 * A376942 A376943 A376944

Keyword

nonn

Author

Scott R. Shannon, Oct 12 2024

Status

approved