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A264848
a(n) is least number > 0 such that the concatenation of a(1) ... a(n) is 19-gonal: (17n^2 - 15n)/2.
7
1, 9, 224, 631909, 58000804596, 61688194098028272863216, 2514637794509678630513616176470588235294117671, 941048382372874985200592647058823529411764708485294117647058823529411764705882352941176469
OFFSET
1,2
LINKS
EXAMPLE
1, 19, 19224, 19224631909 are 19-gonal.
PROG
(PARI) enneadecagonal(n)=ispolygonal(n, 19)
first(m)=my(s=""); s="1"; print1(1, ", "); for(i=2, m, n=1; while(!enneadecagonal(eval(concat(s, Str(n)))), n++); print1(n, ", "); s=concat(s, Str(n)))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Anders Hellström, Nov 26 2015
EXTENSIONS
a(5)-a(8) from Chai Wah Wu, Mar 16 2018
STATUS
approved