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A177201 Multiples of nontrivially polygonal numbers A090466. 1
6, 9, 10, 12, 15, 16, 18, 20, 21, 22, 24, 25, 27, 28, 30, 32, 33, 34, 35, 36, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 63, 64, 65, 66, 68, 69, 70, 72, 75, 76, 78, 80, 81, 82, 84, 85, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Multiples of numbers in the array of A057145 below the second row (which has every positive integer) and right of the 2nd column (which has every positive integer). That is, multiples of every triangular number >3, every square >4, every pentagonal number >5, every hexagonal number >6, every heptagonal number >7, every octagonal number >8, every 9-gonal (nonagonal) number >9, and so forth.

Nontrivially polygonal numbers {6, 9, 10, 12, 15, 16, 18, 21, 22, 24, 25, 27, 28, 30, 33, 34, 35, 36, 39, 40, 42, 45, 46, 48, 49,...} UNION 2*nontrivially polygonal = {12, 18, 20, 24, 30, 32, 36, 42, 44, 48, 50, 54, 56, 60, 66, 68, 70, 72, 78, 80, 84, 90, 92, 96, 98, ...} UNION 3*nontrivially polygonal = {18, 27, 30, 36, 45, 48, 54, 63, 66, 72, 75, 81, 84, 90, 99, ...} UNION 4*nontrivially polygonal = {24, 36, 40, 48, 60, 64, 72, 84, 88, 96, 100, ...} UNION 5*nontrivially polygonal = {30, 45, 50, 60, 75, 80, 90, ...} UNION 6*nontrivially polygonal = {36, 54, 60, 72, 90, 96, ...} UNION 7*nontrivially polygonal = {42, 63, 70, 84, ...} and so forth.

LINKS

Table of n, a(n) for n=1..65.

FORMULA

{A057145 * j for j = 1, 2, 3, 4, 5, ...} = {j * ((n-2)*k^2-(n-4)*k)/2, j>0, n > 2, k > 2}.

CROSSREFS

Cf. A057145, A090466, complement is A177202.

Sequence in context: A241913 A053869 A085275 * A090466 A090428 A039725

Adjacent sequences:  A177198 A177199 A177200 * A177202 A177203 A177204

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, May 04 2010

STATUS

approved

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Last modified November 21 11:35 EST 2019. Contains 329370 sequences. (Running on oeis4.)