OFFSET
1,2
COMMENTS
Conjecture: the only numbers for which 5 addends are needed are 15, 23, 55, 62, 71.
The numbers mentioned in the conjecture are also the first five terms of A111151. - Omar E. Pol, Mar 01 2022
EXAMPLE
a(1) = 1 because 1 can be represented with a single positive perfect power: 1 = 1^2.
a(2) = 2 because 2 can be represented with two (and not fewer) positive perfect powers with different exponents: 2 = 1^2 + 1^3.
a(6) = 3 because 6 can be represented with three (and not fewer) positive perfect powers with different exponents: 6 = 2^2 + 1^3 + 1^4.
a(7) = 4 because 7 can be represented with four (and not fewer) positive perfect powers with different exponents: 7 = 2^2 + 1^3 + 1^4 + 1^5.
a(15) = 5 because 15 can be represented with five (and not fewer) positive perfect powers with different exponents: 15 = 2^2 + 2^3 + 1^4 + 1^5 + 1^6.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alberto Zanoni, Feb 22 2022
STATUS
approved