Sequences
which I have corrected in the OEIS
The OEIS is
the best resource for integer sequences on the internet and is maintained and
presided over by Neil Sloane with the assistance of an editorial panel of
around 70 mathematicians and computer programmers. It currently contains around
200000 sequences, and those listed below are ones that ‘slipped through the
net’ and which I corrected:
1. 
Units digits of the perfect numbers – a(20)
corrected. 




2. 
a(n) = 1 unless n is a prime or prime power, in which case a(n)
= the prime in question  closed form in terms of the binomial
coefficients corrected. 




3. 
Hypotenuses of more than one Pythagorean triangle 
typo corrected. 




4. 
Possible bases for Pepin’s primality test for Fermat
numbers  incorrect reference to elite primes removed. 




5. 
Number of primitive Pythagorean triangles with leg n
 Incorrect comment (to the effect that the members of this sequence were
also the number of ways in which n could be expressed as the difference of
two coprime squares) removed 




6. 
Centered 9gonal (or nonagonal) numbers. Every third
triangular number, starting with a(1)=1. Closed form corrected to
comply with sequence offset 1. 




7. 
Non tetrahedral numbers. Defining formula corrected. 




8. 
Octagonal pyramidal numbers: n(n+1)(2n1)/2. Incorrect formula deleted. 




9. 
Digital root of n^3. The given fraction contained a spurious, leading 




10. 
(3n+2)^3. First digital root given in the proof in
the comment line corrected. 




11. 
Limit set for operation of repeatedly replacing a number by
the sum of the 4th power of its digits. Erroneous comment regarding
the trajectory terminating conditions corrected. Also, added a zero to the set
of least k’s which return a(n) for consistency with the first term of the
given limit set. Similarly for the number of iterations required to get
there, whilst also taking the opportunity to correct two of the existing
terms. 


