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A264848
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a(n) is least number > 0 such that the concatenation of a(1) ... a(n) is 19-gonal: (17n^2 - 15n)/2.
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6
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1, 9, 224, 631909, 58000804596, 61688194098028272863216, 2514637794509678630513616176470588235294117671, 941048382372874985200592647058823529411764708485294117647058823529411764705882352941176469
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OFFSET
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1,2
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LINKS
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EXAMPLE
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1, 19, 19224, 19224631909 are 19-gonal.
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PROG
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(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)))
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CROSSREFS
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Cf. A051671, A051871 (19-gonal numbers), A061109, A061110, A261696, A264733, A264738, A264776, A264777, A264804, A264842, A264849.
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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