A061727 A000217 interleaved with A061726.

1, 4, 3, 12, 6, 30, 10, 50, 15, 60, 21, 84, 28, 140, 36, 180, 45, 180, 55, 220, 66, 330, 78, 390, 91, 364, 105, 420, 120, 600, 136, 680, 153, 612, 171, 684, 190, 950, 210, 1050, 231, 924, 253, 1012, 276, 1380, 300, 1500, 325, 1300, 351, 1404, 378, 1890, 406

Offset: 1

Author

Jason Earls, May 05 2001

Keywords

• nonn
• dumb
• easy

References

• Norman Sullivan, Test Your Own IQ, Workman Publishing Co. New York, NY, 1994, pp. 48, 50.

Links

• Harry J. Smith, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A000217, A061726.

Programs

Mathematica

Array[{#, (4 + Boole[EvenQ@ #]) #} &@ PolygonalNumber@ # &, 28] // Flatten (* Michael De Vlieger, Jul 01 2018 *)

PARI

{ f="b061727.txt"; for (n=1, 1000, a=n*(n + 1)/2; if (a%2, t=a*4, t=a*5); write(f, 2*n - 1, " ", a); write(f, 2*n, " ", t) ) } \\ Harry J. Smith, Jul 27 2009

Extensions

More terms from David Wasserman, Jun 25 2002