OFFSET
1,3
FORMULA
For n > 4, a(n) is the least number k >= n(n+1)/2 such that k - gpp(k) >= n(n-1)/2, where gpp(k) is the largest prime power dividing k. - Charlie Neder, Feb 03 2019
PROG
(PARI) a(n) = if(n<5, return([1, 0, 6, 14][n])); for(k=n*(n+1)/2, oo, if(k-if(1==k, k, my(f=factor(k)); vecmax(vector(#f[, 1], i, f[i, 1]^f[i, 2]))) >= n*(n-1)/2, return(k))); \\ Jinyuan Wang, May 03 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Mar 28 2003
EXTENSIONS
Corrected and extended by David Wasserman, Jun 08 2004
Offset changed to 1 by Jinyuan Wang, May 02 2020
STATUS
approved