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A272267 The union of centered square numbers (A001844) and centered 9-gonal numbers (A060544). 2
1, 5, 10, 13, 25, 28, 41, 55, 61, 85, 91, 113, 136, 145, 181, 190, 221, 253, 265, 313, 325, 365, 406, 421, 481, 496, 545, 595, 613, 685, 703, 761, 820, 841, 925, 946, 1013, 1081, 1105, 1201, 1225, 1301, 1378, 1405, 1513, 1540, 1625, 1711, 1741, 1861, 1891 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

FORMULA

Conjectures:

  a(n) = a(n-1)+2*a(n-5)-2*a(n-6)-a(n-10)+a(n-11) for n>11.

  G.f.: x*(1+4*x+5*x^2+3*x^3+12*x^4+x^5+5*x^6+4*x^7+x^10) / ((1-x)^3*(1+x+x^2+x^3+x^4)^2).

PROG

(PARI)

cpg(m, n) = m*n*(n-1)/2+1 \\ n-th centered m-gonal number

cpgr(m, r) = n=1; L=List(); while((t=cpg(m, n))<r, listput(L, t); n++); Vec(L)

cpgcpgs(p, q, r) = setunion(cpgr(p, r), cpgr(q, r))

cpgcpgs(4, 9, 2000)

CROSSREFS

Cf. A001844, A060544, A272266.

Sequence in context: A313450 A292268 A309593 * A195735 A061145 A321558

Adjacent sequences:  A272264 A272265 A272266 * A272268 A272269 A272270

KEYWORD

nonn

AUTHOR

Colin Barker, Apr 24 2016

STATUS

approved

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Last modified September 21 17:46 EDT 2019. Contains 327273 sequences. (Running on oeis4.)