A122799 A P_7-stuttered arithmetic progression with a(n+1)=a(n) if n is not a heptagonal number, a(n+1)=a(n)+2 otherwise.

1, 1, 3, 5, 7, 9, 11, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179, 181, 183, 185, 187

Offset

1,3

Comments

P_7(i) = the i-th heptagonal number.

Links

Table of n, a(n) for n=1..100.

Douglas E. Iannucci and Donna Mills-Taylor. On Generalizing the Connell Sequence. Journal of Integer Sequences 2 (1999), Article 99.1.7.

Grady D. Bullington, The Connell Sum Sequence, J. Integer Seq. 10 (2007), Article 07.2.6. (includes direct formula for a(n))

Formula

a(n) = A045930(n)-n+1.

Prog

(PARI) isHeptag(n) = {if (! issquare(40*n+9, &res), return (0)); if ((res + 3) % 10, return (0), return (1)); }
lista(m) = {aa = 1; for (i=1, m, print1(aa, ", "); if (! isHeptag(i), aa += 2); ); } \\ Michel Marcus, Apr 01 2013

Crossrefs

Cf. A001614, A122793, A122794, A122795, A122796, A122797, A122798, A122800.

Sequence in context: A371215 A103701 A206544 * A345425 A362022 A162495

Adjacent sequences: A122796 A122797 A122798 * A122800 A122801 A122802

Keyword

nonn,easy

Author

Grady Bullington (bullingt(AT)uwosh.edu), Sep 14 2006

Extensions

Definition corrected by Michel Marcus, Apr 01 2013

Status

approved