login
A279664
Constant whose Engel Expansion is A007775.
0
1, 1, 5, 6, 9, 0, 5, 1, 5, 3, 7, 5, 4, 0, 2, 8, 9, 5, 4, 5, 0, 1, 3, 4, 5, 8, 1, 5, 5, 7, 2, 3, 2, 1, 4, 6, 5, 3, 5, 2, 5, 5, 4, 0, 2, 8, 9, 4, 8, 7, 9, 5, 3, 6, 4, 7, 0, 0, 3, 9, 9, 3, 8, 9, 5, 9
OFFSET
1,3
COMMENTS
This one constant is enough information to uniquely reconstruct A007775.
There appears to be a general expression for higher sets of k-rough numbers.
FORMULA
Define an indexing function over the primes and 7^2.
P(n) = prime(n) for n<16, 49 for n=16, prime(n-1) for n>16.
a = Pi^4*Sum_{k>=0}Sum_{n=1..8} 2^(4-n-8*k)*15^(-n-8*k)/(Prod_{m=1..8} Gamma( P(2+m+n)/30 + k)). - Benedict W. J. Irwin, Dec 16 2016
EXAMPLE
1.15690515375402895450134581557232146535255402894879536470039938959...
MATHEMATICA
Prime7[n_] := If[n < 16, Prime[n], If[n == 16, 7^2, Prime[n - 1]]];
RealDigits[N[Pi^4*Sum[Sum[2^(4-n-8*k)*15^(-n-8*k)/Product[Gamma[ Prime7[2+m+n]/30+k], {m, 1, 8}], {n, 1, 8}], {k, 0, Infinity}], 100]][[1]]
CROSSREFS
Cf. A007775.
Sequence in context: A019149 A172997 A244274 * A230461 A277522 A019598
KEYWORD
nonn,cons
AUTHOR
STATUS
approved